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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
Servings: 6 -8 servings


  • 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


  • 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.
  • 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.
  • 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.
  • 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.
Craving more veg-friendly recipes? Shop our collection of vegetarian and vegan cookbooks!

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
    Josephine Rock Williams
    November 28, 2017 at 6:07 am

    I liked the sound of this recipe so much that I made a double batch of it! My husband & I LOVED it!!!!!!!! I baked both of them and froze one for another day. It took a little time to make until my husband suggested using kitchen sissors to cut the stems from the leaf!!!!! And I DO NOT LIKE grating cheese. The meal is so yummy and FILLING!!!
    We are attempting to go vegan and this was the first recipe that I tried, and it is a keeper!!!!!!

    • Reply
      Katie Trant
      December 2, 2017 at 8:35 am

      Yay! So glad you loved this recipe as much as we do, Josephine!

  • Reply
    January 13, 2018 at 12:03 pm

    My vegetarian in-laws are coming and I want to have some meals in the freezer to pop in the oven. Did these taste good out of the freezer Josephine?

  • Reply
    January 20, 2018 at 8:32 pm


  • Reply
    Marsha Gainey
    June 17, 2018 at 11:31 am

    3 stars
    This was good. It makes a ton, so I had lots of leftovers. I subbed kale because I don’t like Swiss chard, and I subbed mozzarella for the fontina because I forgot to buy fontina at the store. Definitely will make again.

  • Reply
    December 1, 2018 at 3:37 pm

    With the topping,I ended up with a tomato-based sauce, which is not what the photo appears to show. It’s way too tomato-ey with a whole 28-oz can of tomatoes. The mushrooms and chard are lost, indistinguishable. I’m putting this sauce in the freezer and starting again with the mushrooms and chard, adding just a single fresh tomato.

  • Reply
    December 17, 2018 at 3:42 pm

    5 stars
    This was delicious! My husband and I gobbled it up. We added tofurkey sausages to give us some protein. Some beans could have worked too. Can’t wait to eat leftovers tonight!

  • Reply
    January 6, 2019 at 5:51 pm

    5 stars
    I made this tonight and will definitely make it again. I used spinach I/o Swiss chard because I’m not familiar with Swiss chard. I added a little worschestershire sauce which I do a lot when cooking mushrooms. The other deviation I did was use Trader Joe’s polenta that comes in a plastic and looks like a big sausage. I just sliced it and lined my backing pan with it. It worked out great.

  • Reply
    March 2, 2019 at 10:50 am

    5 stars
    This is really delicious and filling! A great dish for a winters night. My husband and I appreciated the leftovers.

  • Reply
    April 2, 2019 at 10:48 pm

    This is such a great recipe ! I made a batch to eat all week for lunch, and I looked forward to it every day! Thanks for an easy healthy option.

  • Reply
    Reena Patel
    June 1, 2019 at 10:36 am

    5 stars
    This is one of my go to dishes!

  • Reply
    Patricia Fulwiler
    June 19, 2019 at 6:53 pm

    5 stars
    So very good, I make this once a month the flavors are so good together. And so healthy

  • Reply
    November 24, 2019 at 4:37 pm

    5 stars
    Excellent I love the flavors and how it all comes together and very healthy

  • Reply
    July 21, 2020 at 8:19 pm

    5 stars
    This was SO GOOD.

  • Reply
    January 23, 2021 at 8:05 pm

    5 stars
    I veganized this and left out the oil. It was fabulous and I’ll definitely make again!

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