Ham & Potato Casserole

Position oven rack in middle of oven; preheat to 375 degrees F. Lightly coat a 9-by-13-inch broiler-safe baking dish with cooking spray.

Whisk flour and 1/2 cup milk in a small bowl until smooth. Bring the remaining 3 1/2 cups milk to a simmer in a medium saucepan over medium-high heat. Whisk in the flour mixture. Reduce heat to medium; simmer, whisking often, until slightly thickened, about 5 minutes. Remove from heat. Gradually whisk in Cheddar, mozzarella and pepper, whisking until melted and smooth.

Combine hash browns (or shredded potatoes), peas and ham in a large bowl. Add the cheese mixture; stir to coat. Spoon the mixture into the prepared baking dish. Cover with foil. Bake until hot throughout and bubbly around the edges, 55 to 65 minutes. Remove foil. Switch oven to broil; broil the casserole until the top is lightly browned, 3 to 4 minutes.