macaroni & cheese gratin

for my halloween spookfest last weekend, I decided that appetizers just weren't hearty enough for my guests, so I made macaroni and cheese gratin. that's one of those things that looks pretty when dolled up with herb broiled tomatoes and buttery breadcubes on top. besides, the crunch that comes from the crust mixed with the smooth sauce is perfection.

macaroni & cheese gratin

8 Tablespoons (1 stick) unsalted butter, plus more for dish
6 slices good white bread, crusts removed, torn into 1/2 inch pieces
5 1/2 cups milk
1/2 cup all-purpose flour
2 teaspoons kosher salt
1/4 teaspoon grated nutmeg
1/4 teaspoon freshly ground black pepper
1/4 teaspoon cayenne pepper, or to taste
4 1/2 cups grated sharp cheddar cheese (note: Tillamook or Cabot is best)
1 1/4 cups grated Pecorino Romano cheese
1 pound large elbow macaroni

3 hothouse tomatoes, sliced

Heat oven to 375 degrees. Butter a 3-quart casserole dish; set aside. Place bread in a medium bowl. In a small saucepan over medium heat, melt 2 Tablespoons butter. Pour butter into bowl with bread, and toss. Set breadcrumbs aside.

In a medium saucepan set over medium heat, heat milk (note: this step is important). Melt remaining 6 Tablespoons butter in a high-sided skillet over medium heat. When butter bubbles, add flour. Cook, whisking, 1 minute.

While whisking, slowly pour in hot milk. Continue cooking, whisking constantly, until the mixture bubbles and becomes thick (note: cook over medium-low heat. I think the sauce will be more smooth if you don't rush the thickening process.)

Remove pan from heat. Stir in salt, nutmeg, black pepper, cayenne pepper, 3 cups cheddar cheese, and 1 cup Pecorino Romano; set cheese sauce aside.

Fill a large saucepan with water; bring to a boil. Add macaroni; cook 2 to 3 minutes less than manufacturer's directions, until the outside of pasta is cooked and the inside is underdone. (Different brands of macaroni cook at different rates; be sure to read the instructions.) Transfer macaroni to a colander, rinse under cold running water, and drain well. Stir macaroni into the reserved cheese sauce.

Pour mixture into prepared dish. Sprinkle remaining 1 1/2 cups cheddar cheese, 1/4 cup Pecorino Romano, and breadcrumbs over top.

Lay sliced tomatoes on a cookie sheet. Drizzle with olive oil, coarse salt, freshly ground pepper and thyme leaves. Broil for about 10 minutes until softened. Let cool for a few minutes and then arrange on top of the gratin (over the breadcrumbs).

Bake until browned on top, about 30 minutes. Transfer dish to a wire rack to cool 5 minutes; serve hot.