This zucchini casserole eats like a gratin topped with Parmesan cheese and toasted bread crumbs for an easy side dish everyone loves.
My grandma’s recipe box is a treasure trove of simple-to-make, feel good comfort food dishes. So when I came across this old fashioned zucchini casserole recipe, it was a no-brainer to make and use up some my garden’s zucchini stock pile.
Like my tuna noodle casserole recipe, this zucchini casserole goes gratin-style, with a nippy Parmesan cheese bite and crispy, crunchy bread crumb topping. But what sets this gratin side dish apart from others is it won’t weigh you down. Instead of a traditional butter, milk, and flour bechamel sauce or roux, this recipe uses sour cream mixed with an egg yolk for the creamy binder base.
What’s In Zucchini Casserole
With just a handful of ingredients, this recipe demands they be good quality. Choose medium size zucchini with soft, tender skins. Depending on the size, you’ll need two or three.
- Zucchini (to make 8 cups sliced)
- Kosher salt and freshly ground black pepper
- Sour cream
- Egg yolk
- Grated or shaved Parmesan cheese
- Fresh chives
- Dry bread crumbs or panko bread crumbs
How to Make Zucchini Casserole
For even cooking, cut the zucchini into uniform slices. I use this handheld mandoline to evenly slice the zucchini. You’ll need about 8 cups of sliced zucchini, but if you have a bit more or less, don’t stress, just toss it in.
Cook the zucchini in a large skillet. Cook the zucchini just until it softens, but doesn’t become limp. You want to retain the green vibrancy of the skin and tender bite.
Make the Gratin Sauce
Make the sour cream and egg yolk binder. Instead of a traditional roux or bechamel made with butter, flour, and milk or broth, egg yolk acts as the binder, firming up the sour cream as it cooks with grated Parmesan cheese.
Allow the melted butter to cool before adding to the sour cream and egg yolk mixture. Hot butter plus cold eggs creates scrambled chunks. To avoid this, make sure the melted butter has cooled before mixing it into the sour cream and adding the egg.
Fold the sour cream mixture and fresh chives into the skillet with the warm zucchini. Toss the zucchini with the creamy mixture until well coated and the cheese begins to melt. Add the fresh chopped chives for an onion-y bite.
Sprinkle With the Crispy Topping
Mix dried bread crumbs or panko with melted butter. Drizzling melted butter into the bread crumb and Parmesan cheese mixture creates a crisp and toasty topping when exposed to the heat of the oven. Add the remaining chopped chives for another layer of flavor and color.
Bake covered with foil, then raise the heat and uncover to bronze and crisp. Transfer the zucchini to a baking dish and top evenly with the bread crumb mixture. Bake covered at 375°F for the insides to warm evenly. Then, remove the foil and raise the heat to 475° F to brown to get the best toasted topping.
Zucchini Casserole Recipe Substitutions
- Use full fat Greek yogurt instead of sour cream. I’d stay away from lower fat options that contain more water, so this casserole doesn’t get watery.
- Sauté chopped yellow onion with the zucchini instead of using chopped chives.
- Add 1 clove pressed garlic for more zing.
- Try adding herbs like thyme, dill, or tarragon.
- Use a melty white cheese like Swiss or gruyere instead of the Parmesan, or, try goat cheese.
- Add 1 tablespoon grated lemon zest into the bread crumb mixture for a fresh, gremolata taste.
What to Serve With Zucchini Casserole
- Juicy Turkey Breast
- Oven Roasted Chicken with Lemon Rosemary Garlic Butter
- Easy Chicken Piccata
- Stuffed Pork Chops
- The Best Baked Chicken Breast
If you make this recipe, please let me know! Leave a ⭐️⭐️⭐️⭐️⭐️ rating on this recipe below and leave a comment, take a photo and tag me on Instagram with #foodiecrusheats.
Zucchini Casserole with Parmesan
- 8 cups sliced zucchini , from 2-3 medium zucchini
- 3 tablespoons butter , divided
- 1 teaspoon kosher salt , divided
- ¼ teaspoon freshly ground black pepper
- ⅓ cup sour cream
- 1 large egg yolk , whisked
- ½ cup grated Parmesan cheese , divided
- 2 tablespoons chives , divided
- ¼ cup dried bread crumbs
- Preheat the oven to 375°F.
- Melt 1 tablespoon of the butter in a large skillet over medium heat. Add the zucchini slices and season with ½ teaspoon kosher salt and the black pepper. Cook, stirring occasionally, until the zucchini is softened but still vibrant and green, about 10 minutes. Remove from the heat.
- While the zucchini is cooking, melt 2 tablespoons of the butter in the microwave or on the stove top, and set aside to cool. In a medium bowl, mix 1 tablespoon of the cooled, melted butter with the sour cream, ½ teaspoon kosher salt, and then the egg yolk. Fold into the zucchini mixture with ¼ cup of the grated Parmesan cheese and 1 tablespoon of the chives.
- Spray a 7 X 11-inch or 2-quart baking dish with cooking spray, then transfer the zucchini mixture to the dish. In a small bowl, combine the bread crumbs with the remaining melted butter and Parmesan cheese, plus the remaining chopped chives. Sprinkle the bread crumb mixture evenly over the zucchini. Cover with foil and bake until warmed through and the cheese has started to melt, about 15-20 minutes. Remove the foil and raise the oven temperature to 450°F. Bake until the top is browned and the filling is bubbling at the edges, about 10 minutes. Sprinkle with more fresh chives if desired, and serve.
- Substitute plain, whole milk Greek yogurt for the sour cream if desired.
More Great Side Dish Ideas
- Easy 5-Minute Parmesan Zucchini
- Easy Creamy Au Gratin Potatoes
- Sautéed Spinach with Garlic
- 5-Ingredient Stovetop Creamed Spinach
- Broccoli Casserole with Crispy Onions
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