- 3 Tablespoons unsalted butter, plus 1.5 Tbsp butter extra for topping
- 3 Tablespoons olive oil
- 2 large yellow onions, cut in 1/2 and sliced (3 onions okay, too)
- 3 large zucchini, sliced 1/4-inch thick (4 zucchini okay, too)
- 2 teaspoons kosher salt
- 1/2 teaspoon freshly ground black pepper
- 1/4 teaspoon ground nutmeg
- 2 tablespoons all-purpose flour
- 1 cup hot milk
- 3/4 cup fresh bread crumbs
- 3/4 cup grated Gruyere (or substitute Swiss cheese)
- Preheat the oven to 400 degrees F.
- Melt the butter in olive oil in a very large (12-inch) saute pan and cook the onions over medium heat for 10-15 minutes, or until tender but not browned. Add the zucchini and cook, covered, for about 5 minutes, or until tender. Add the salt, pepper, and nutmeg and cook uncovered for 2 more minutes. Stir in the flour. Add the hot milk and cook over low heat for a few minutes, until it makes a sauce. Pour the mixture into an 8 by 10-inch baking dish.
- Combine the bread crumbs and Gruyere in food processor. Add melted butter (1.5 Tbsp) and process until crumbly. Sprinkle evenly on top of the zucchini mixture.
- Bake for 20 minutes, or until bubbly and browned.