Ingredients
6 tablespoons unsalted butter
1 cup fresh breadcrumbs
1/4 cup grated Parmesan
8 ounces sliced cremini mushrooms
1/2 cup unbleached all-purpose flour
6 cups 2-percent milk
3/4 pound elbow macaroni
3 cups grated Fontina
1 cup grated Gruyere
2 teaspoons chopped fresh thyme leaves
Kosher salt and freshly ground pepper
Preparation
Heat broiler. In a large straight-sided, oven-safe skillet, melt butter. Remove 1 tablespoon butter and combine with breadcrumbs and Parmesan.
Add mushrooms to skillet and cook until softened. Whisk in flour and cook, stirring, 1 minute. Very gradually whisk in milk and bring to a simmer. Add macaroni and cook, stirring constantly and scraping bottom of pan, until tender, about 6 minutes. Remove from heat, stir in remaining cheese and the thyme, and season with salt and pepper. Top with breadcrumb mixture and broil until golden brown, 1 to 2 minutes.
