Broccoli & Cauliflower Gratin

4 T. (1/2 stick) unsalted butter, plus more for dish
1 medium head cauliflower (about 2 lbs.), cored and sliced 1/4" thick
1 large head broccoli (about 1-1/2 lbs.), trimmed and sliced 1/4" thick
6 T. all-purpose flour
3 c. whole milk
1/4 t. freshly grated nutmeg
8 oz. Gruyere cheese, grated (about 2 c.), divided
Kosher salt and freshly ground pepper

Preheat oven to 375 degrees. Butter a shallow 3-qt. baking dish. Arrange cauliflower and broccoli in the prepared dish.

Melt butter in a medium saucepan over medium heat. Add flour and cook, stirring, 2 minutes (do not let it darken). Slowly whisk in milk. Simmer, whisking occasionally, until slightly thickened, 3-4 min. Remove from heat and stir in nutmeg and 1-1/4 c. cheese. Season with salt and pepper. Pour over vegetables. Sprinkle with remaining 3/4 c. cheese.

Cover loosely with aluminum foil and bake for 15 min. Remove foil; bake until vegetables are tender and the top is golden brown, 20-25 min. Let stand 10 min. before serving.

Makes 8-10 servings.

Adapted from County Living magazine, Nov. 2019, p. 103.