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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


  • 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.

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

    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.

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