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Savory Parmesan Zucchini Casserole Recipe with Caramelized Onions and Gruyère

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A comforting and flavorful zucchini casserole layered with sweet caramelized onions, nutty Parmesan, and creamy Gruyère cheese, perfect for easy weeknight dinners.

Ingredients

Scale
  • 4 medium zucchinis, thinly sliced (about 1/4-inch thick)
  • 2 large yellow onions, thinly sliced
  • 1 cup grated Parmesan cheese (Parmigiano-Reggiano recommended)
  • 1 cup shredded Gruyère cheese
  • 3 cloves garlic, minced
  • 3 tablespoons extra virgin olive oil
  • 1 cup heavy cream (or half-and-half for lighter version)
  • 2 large eggs, lightly beaten
  • 1 teaspoon fresh thyme, chopped (optional)
  • Salt and pepper to taste (kosher salt recommended)
  • 1/2 cup panko breadcrumbs (or almond flour/gluten-free breadcrumbs for gluten-free option)

Instructions

  1. Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with olive oil or butter.
  2. Heat 2 tablespoons olive oil in a large skillet over medium-low heat. Add the sliced onions and a pinch of salt. Stir occasionally for about 25-30 minutes until deep golden brown and soft. Add a splash of water if onions start to stick.
  3. While onions cook, thinly slice the zucchinis. If watery, sprinkle with salt and let sit in a colander for 10 minutes, then pat dry with paper towels.
  4. In a medium bowl, whisk together the eggs, heavy cream, minced garlic, chopped thyme, salt, and pepper.
  5. In a large bowl, gently toss the sliced zucchini with the caramelized onions, grated Parmesan, and shredded Gruyère. Pour in the egg and cream mixture and stir gently until evenly coated.
  6. Pour the zucchini mixture into the prepared baking dish, spreading evenly. Sprinkle the breadcrumbs evenly over the top.
  7. Bake for 35-40 minutes, until the top is golden brown and the casserole is set (a knife inserted in the center should come out clean). Tent loosely with foil if top browns too quickly.
  8. Let the casserole cool for about 10 minutes before serving.

Notes

Caramelizing onions slowly is key for deep flavor. Salting and draining zucchini prevents sogginess. Breadcrumb topping adds a crunchy texture. The casserole reheats well; warm gently to avoid cheese separation. For gluten-free, substitute panko with almond flour or gluten-free breadcrumbs. Vegetarian cheeses should be rennet-free. Variations include adding mushrooms, Italian sausage, or different herbs like rosemary or sage.

Nutrition

Keywords: zucchini casserole, Parmesan, Gruyère, caramelized onions, easy dinner, vegetarian, gluten-free option, comfort food

Find it online: https://bakebelle.com/savory-parmesan-zucchini-casserole-recipe-with-caramelized-onions-and-gruy-e-re-perfect-for-easy-dinners/