Zucchini Gratin With Cheddar Cheese

This zucchini gratin is a flavorful side dish casserole with extra richness from the cheddar cheese. A gratin is a baked dish with a creamy sauce and crunchy topping, and is always a nice way to make a fancy side dish out of everyday vegetables. If you or your neighbors have an abundance of garden-fresh summer squash or zucchini, this is an excellent way to use it.


  • 8 tablespoons (4 ouncesunsalted butter, divided
  • 1 large onion, chopped
  • 2 pounds zucchini, sliced (about 6 cups)
  • 2 tablespoons all-purpose flour
  • 1 cup milk
  • 1 teaspoon kosher salt, or to taste
  • 1/4 teaspoon mustard powder
  • Freshly ground black pepperto taste
  • 1 pinch nutmeg, optional
  • 1 cup shredded cheddar cheese
  • 4 slices bacon, cooked until crisp, drained, crumbled, optional
  • 1 cup soft, fresh breadcrumbs


  1. Gather the ingredients.

  2. Preheat the oven to 350 F. Butter a 1 1/2-quart baking dish.

  3. In a large skillet over medium heat, melt 4 tablespoons of the butter. Add the chopped onion and sauté, stirring, until it is tender and translucent.

  4. Add the sliced zucchini to the skillet and reduce the heat to low. Cover the pan and cook for 10 to 15 minutes, or just until tender. Remove the vegetables to a bowl with a slotted spoon and set aside.

  5. Add 2 tablespoons of the butter to the skillet and melt over medium-low heat. Add the flour and cook, stirring constantly, for 2 minutes.

  6. Gradually add the milk to the flour and butter roux and continue cooking until thickened, stirring constantly. Add the kosher salt, mustard powder, and black pepper, along with a dash of nutmeg, if desired. Taste the sauce and adjust the seasonings, as needed.

  7. There will be some excess liquid from the cooked zucchini, so use a slotted spoon to transfer the zucchini and onion back to the skillet. Stir the mixture gently to coat the zucchini with the sauce.
  8. Turn the zucchini and sauce mixture into the prepared baking dish. Sprinkle the shredded cheese over the casserole along with the cooked crumbled bacon, if using.

  9. Melt the remaining 2 tablespoons of butter and toss with the breadcrumbs. Sprinkle over the zucchini casserole.

  10. Bake the gratin in the preheated oven for 20 to 25 minutes, or until the topping is browned and the casserole is bubbling around the edges.

Zucchini Gratin With Cheddar Cheese

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