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Rustic Polenta Casserole with Mushrooms and Swiss Chard

Rustic Polenta Casserole with Mushrooms and Swiss Chard

Photos by Emily Caruso

I am endlessly fascinated by America’s Test Kitchen’s magazines and cookbooks. I love that they detail the process of recipe development and not just, “Hey, here’s a recipe! It tastes good! Enjoy!” While baking is more of a science than cooking, there is still a science to cooking and it’s interesting to read exactly why frozen peas are better than fresh for most recipes or how different types of potatoes result in different textures in gratins.

The Complete Vegetarian Cookbook is exactly what you’d expect from an America’s Test Kitchen cookbook. The recipes are tried and true and each starts out with a paragraph explaining why it works. There are 700 recipes in this book (YES! Seven-hundred!) and they range from dishes that are naturally meatless, like this polenta casserole, and dishes that are traditionally made with meat, made vegetarian (we’ll be sharing one of those recipes next week). There are cookbooks based on gimmicks and trends that you buy, make a few recipes from, and set aside, and there are cookbooks that you’ll be cooking from 20 years from now—this is the kind of cookbook that’s destined to be a staple in your kitchen.

Swiss Chard
I received an advance copy of the book several weeks ago, so I’ve already had the chance to make quite a few recipes from it and this polenta casserole is one of my favorites. It tops a batch of creamy Parmesan polenta with a layer of meaty mushrooms and chard cooked in tomato sauce. The thing I love about polenta casseroles is that while they’re filling and hearty and everything you love about comfort food, they’re actually not that heavy—eating a serving of this casserole doesn’t make you feel uncomfortably full and weighed down like eating a serving of lasagna might. I should also note that we had this for dinner 3 nights in a row; the leftovers kept well in the fridge and they were just as delicious as the first day I made it. While the recipe does take a little bit of time that first day, the subsequent days of leftovers (woo hoo, no cooking!) made up for it.


Rustic Polenta Casserole with Mushrooms and Swiss Chard

Rustic Polenta Casserole with Mushrooms and Swiss Chard

A hearty meatless casserole from America’s Test Kitchen’s The Complete Vegetarian Cookbook.

  • Prep Time: 10 minutes
  • Cook Time: 1 hour 25 minutes
  • Total Time: 1 hour 35 minutes
  • Yield: 6-8 servings 1x


  • 3 cups water
  • 1 cup whole milk
  • Salt and pepper
  • 1 cup coarse-ground polenta
  • 2 ounces Parmesan cheese, grated
  • 3 tablespoons unsalted butter
  • 3 tablespoons extra-virgin olive oil
  • 1 onion, chopped fine
  • 1 1/2 pounds white mushrooms, trimmed and sliced thin
  • 3 garlic cloves, minced
  • 1 tablespoon minced fresh thyme or 1 teaspoon dried
  • 1 (28-ounce) can diced tomatoes
  • 8 ounces Swiss chard, stemmed and cut into 1-inch pieces
  • 4 ounces fontina cheese, shredded


  1. Adjust oven rack to middle position and heat oven to 400ºF. Bring water and milk to boil in large saucepan over medium-high heat. Stir in 1 teaspoon salt. Slowly pour polenta into liquid in steady stream while stirring back and forth with wooden spoon. Reduce to gentle simmer, cover, and cook, stirring often, until mixture has uniformly smooth, thick consistency, 15 to 20 minutes. Off heat, stir in Parmesan and butter, and season with salt and pepper to taste. Pour polenta into 13 by 9-inch baking dish and smooth into even layer.
  2. Meanwhile, heat oil in 12-inch skillet over medium heat until shimmering. Add onion and 1/2 teaspoon salt and cook until onion is softened, about 5 minutes. Add mushrooms and cook until they have released their liquid and are well browned, about 25 minutes.
  3. Stir in garlic and thyme and cook until fragrant, about 30 seconds. Stir in tomatoes and their juice, bring to simmer, and cook, stirring occasionally, until sauce has thickened, about 10 minutes. Stir in chard, 1 handful at a time, and cook until wilted, 2 to 4 minutes. Season with salt and pepper to taste.
  4. Spread mushroom mixture evenly over polenta, then sprinkle with fontina. Bake casserole until warmed through and cheese is melted, 10 to 15 minutes. Let cool for 5 minutes before serving.

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Disclosure: We received a review copy of this cookbook from America’s Test Kitchen. Links to Amazon in this post are affiliate links.

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  • Reply
    March 11, 2015 at 9:25 am

    This looks delicious and I appreciate the review. However, I think it’s worth noting that this is not health food. With the whole milk and all that cheese this dish is a land mine of saturated fat and cholesterol, which to me cancels out the benefits of the chard and mushrooms. Great photos and nicely presented. I have always trusted America’s Test Kitchen and will definitely check this book out should it be back in stock. Thanks!

    • Reply
      September 14, 2016 at 8:57 pm

      really? 4 oz of fontina for 6-8 servings is pretty light. Plus 2 oz of parmesan which is a dry cheese, that doesn’t seem like too much to me!

  • Reply
    Jessie : Kitschen Cat
    March 11, 2015 at 9:54 am

    This looks to die for! Polenta is such a fun ingredient and I definitely don’t cook with it enough!

  • Reply
    Sam @ PancakeWarriors
    March 11, 2015 at 10:08 am

    this sounds fantastic. I love to pair mushrooms with greens such a great combo!! Polenta is great for casseroles! I made a Moroccan polenta casserole and it was my favorite casserole so far this year. I can’t wait to try this version!

  • Reply
    Traci | Vanilla And Bean
    March 11, 2015 at 10:46 am

    Thank you for sharing this, Kiersten! This casserole looks fabulous. I’m all about polenta and mushrooms because they just taste so good together; a good mix of flavor and texture. Looking forward to checking out ATK new cook book! Very cool they’ve produced a book focused exclusively on veg and vegan cooking!

  • Reply
    Chelsea @ Chelsea's Healthy Kitchen
    March 11, 2015 at 11:43 am

    I actually just tried making polenta at home for the first time this week after having it at a restaurant a few weeks ago. My first attempt was pretty good, but I’m excited to try it in more recipes like this one. Also, the new ATK vegetarian cookbook sounds just fantastic. I love reading details about the cooking process in a cookbook too.

  • Reply
    Sarah @ Making Thyme for Health
    March 11, 2015 at 11:55 am

    Wow, this looks so good! I’m actually not familiar with America’s Test Kitchen but my grandma is always telling me about it, lol. Their vegetarian cookbook sounds awesome. I’ll definitely have to check it out!

  • Reply
    March 11, 2015 at 1:26 pm

    Thanks for the heads up about America’s Test Kitchen releasing a vegetarian cookbook. I love that show precisely for the reasons you mentioned; breaking down a recipe, offering tips on how to prepare it, the best ingredients to use. even a little history about dishes native to certain areas of the country or other parts of the world. This casserole looks delicious. I’m looking forward to seeing what recipe of theirs you’ll be focusing on next week. They recently featured vegetarian chili and wild rice soup (hint, hint) I like that your blog is sort of a link to all these other great food blogs, not that yours isn’t great on its own 🙂

  • Reply
    Millie | Add A Little
    March 11, 2015 at 3:20 pm

    That photo of the chard is gorgeous – i love how the dark green juxtaposes with the bright stalks!

  • Reply
    Laura (Tutti Dolci)
    March 12, 2015 at 1:04 am

    I love polenta, this is my kind of casserole!

  • Reply
    Cara's Healthy Cravings
    March 12, 2015 at 7:16 am

    Love this!
    I am definitely putting it on my menu plan for next week. Thanks for sharing.

  • Reply
    March 12, 2015 at 12:31 pm

    I love ATK too, and am dying to see this book! This casserole looks amazing! Since I’m trying to lose weight, I would probably cut back on the cheese, butter & oil, or serve smaller portions to reduce the fat and calories a little.

  • Reply
    March 12, 2015 at 10:28 pm

    This polenta casserole looks so homey and comforting and just brimming with veggies I love. This looks delicious!

  • Reply
    Emily | Truefood
    March 13, 2015 at 2:42 pm

    This looks amazing! Polenta in a casserole… it’s definitely a win-win situation. Thanks for sharing, looks delicious.

  • Reply
    March 15, 2015 at 6:28 pm

    The Husband got me this cookbook for my birthday and I am OBSESSED. He totally gets brownie points for this. I want to make everything!! I’m pretty sure it’s right up there with Deborah Madison’s Vegetarian Cooking for Everyone as Best Vegetarian Tome Out There.

  • Reply
    Jennifer @ Delicious Everyday
    March 18, 2015 at 3:14 am

    That casserole is calling out to me. What a beautiful dish!

  • Reply
    March 25, 2015 at 3:55 pm

    Wow, this looks amazing! May have to try it this weekend!

  • Reply
    March 27, 2015 at 11:40 am

    I grew up on polenta with stews, sausages, sauerkraut…you name it. It was a daily staple for my Northern Italian ancestors. I wonder if the recent (easy and delicious!) “instant polenta” would work in this dish? Also, to the poster who talked about it not being very healthy, polenta is typically made with water alone. You could try that…or a skim or fat-free half-and-half. That what I’d try…and hope that it might work! I’ve been a vegetarian for many years now so this sounds like a good way to get my polenta without the meat.

  • Reply
    March 28, 2015 at 8:50 am

    I actually have this cookbook and I’ve made a few recipes from it and this was one of them. The shepards pie was by our favorite one so far (made with lentils instead of soy crumbles). For this recipe, I had kale on hand so I used that and it was delicious. As with most of their recipes, they are very time consuming, but as you say, they last for a few days and keep well. But as some have noted, they are not low-fat/low-cal.

  • Reply
    April 14, 2015 at 1:13 pm

    Hi Kiersten- I was wondering if I could have permission to list your casserole recipe in a list of Favorite Recipe Finds? I’ll be putting it in a monthly newsletter that goes out to my e-mail subscribers for my blog Simple Seasonal. In the newsletter I’ll list the name of your recipe, the name of your blog, and then link people back to your website. Many of my subscribers are CSA members and are always looking for ways to use their chard. Happy cooking! -Rachel

  • Reply
    November 1, 2015 at 2:55 pm

    I agree that this is not a healthy recipe, so I tried my hand at making it healthy (and vegan!).

    For the polenta, I used a “Ready to heat” tube of polenta to save on time (and calories/fat since this recipe calls for butter and whole milk in the polenta) and I decided to incorporate more fall flavors. I added acorn squash and omitted the tomato (and it’s juice), since I thought these two flavors may clash too much. I used veggie broth in it’s place and eliminated the cheeses and instead used a cauliflower-based vegan “alfredo sauce”. Finally, I used kale instead of the chard as that was what I had on hand. I made a lot of changes to this (clearly) but was pretty happy with the result.

    I really fell in love with the idea of having a polenta base for a casserole!

  • Reply
    January 11, 2016 at 1:09 pm

    What a great recipe! I love Swiss chard mushrooms and polenta. Thanks for posting. : )

  • Reply
    August 17, 2016 at 1:45 pm

    Could this dish be frozen? Before or after baking? Thanks!

    • Reply
      August 19, 2016 at 8:36 am

      I haven’t frozen it personally, but in my experience, polenta freezes pretty well. I’d freeze it before baking.

  • Reply
    Cheryl Johnson
    December 4, 2016 at 1:07 am

    Need to be able to print just the recipe.

    • Reply
      December 9, 2016 at 9:37 am

      The print button is back!

  • Reply
    January 14, 2017 at 10:02 am

    Could you use spinach. I don’t ever see chard in my grocery store.

    • Reply
      January 14, 2017 at 10:40 am

      I think spinach would work just fine! Please let us know how it turns out if you give it a try! 🙂

  • Reply
    January 24, 2017 at 8:58 am

    This is terrific! I have made it twice now, and the components are easily prepared ahead. I would like to make it for guests but I am wondering what side dishes would be appropriate given that this already has a leafy vegetable in it. Suggestions welcome!

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