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Squash and Swiss Cheese Casserole

Elizabeth Heiskell Squash casserole
Courtesy / Angie Mosier
Cook Time:
35 mins
Prep Time:
1 hr 5 mins

Chef notes

Squash can grow rampant in Mississippi soil and sometimes planting just a little bit lands folks with mountains of the stuff. Luckily, whether you've frozen your own harvest or bought a bunch for Thanksgiving, this cheesy casserole can be served on turkey day or as part of the leftover spread when all the extended family is still visiting.

Technique tip: Rub your hands with salt before cutting the onion and they will not make your eyes water.

Swap option: Use zucchini if yellow squash is not your favorite.


  • 3 to 4 pounds yellow squash, cut into 1/3-inch slices (about 8½ cups)
  • 2 medium-sized yellow onions, chopped
  • 2 bay leaves
  • 6 flat-leaf parsley sprigs
  • 2 thyme sprigs
  • 1/2 cup salted butter, divided
  • 6 tablespoons all-purpose flour
  • 3 cups whole milk
  • 1/2 teaspoon kosher salt
  • 1 teaspoon seasoned salt
  • 1 teaspoon Worcestershire sauce
  • 1/8 teaspoon ground nutmeg
  • 1/8 teaspoon cayenne pepper
  • 4 large egg yolks, lightly beaten
  • cups Swiss cheese, shredded and divided
  • 1 cup fresh breadcrumbs



Preheat oven to 350°F. Bring a large saucepan of salted water to a boil, add squash, onions, bay leaves, parsley and thyme. Cook until the squash is barely tender, about 10 minutes. Drain and discard the herbs.


While the squash cooks, melt 6 tablespoons of the butter in a medium saucepan over medium-high heat. Add the flour and cook, whisking constantly, about 1 minute. Gradually whisk in the milk and cook, whisking constantly until the mixture boils and thickens, about 11 minutes.


Remove from the heat, whisk in the kosher salt, seasoned salt, Worcestershire sauce, nutmeg and cayenne. Gradually stir about 1/4 of the hot milk mixture into the yolks; add the yolk mixture to the remaining hot milk mixture, stirring constantly.


Return the saucepan to medium low, cook until slightly thickened, about 2 minutes. Whisk in 1 cup of the cheese. Add the sauce to the squash mixture; stir gently to combine. Pour into a lightly buttered, broiler-proof 13-by-9-inch baking dish.


Melt the remaining butter, stir in the breadcrumbs. Sprinkle the breadcrumb mixture and remaining 1/2 cup cheese over the squash. Bake until the top is lightly browned and the sauce is bubbly, about 35 minutes. Increase the oven temperature to broil. Broil 6 inches from the heat until the breadcrumbs are golden brown, about 2 to 3 minutes.