1 pound elbow macaroni
1 quart milk
8 tbsps unsalted butter, divided
½ cup flour
12 ounces Gruyére cheese, grated (4 cups)
8 ounces extra sharp Cheddar, grated (2 cups)
1 tbsp salt
½ tsp freshly ground pepper
½ tsp nutmeg
¾ pound fresh tomatoes (4 small)
1 ½ cups fresh white bread crumbs (5 slices, crusts removed)
Preheat oven to 375ºF.
Drizzle oil into a large pot of boiling salted water. Add the macaroni and cook according to the directions on the package, 6 to 8 minutes. Drain well.
Meanwhile, heat the milk in a small saucepan, but don't boil it. Melt 6 tbsps of butter in a large (4 quart) pot and add flour. Cook over low heat for 2 minutes, stirring with a whisk. While whisking, add the hot milk and cook for a minute or two more, until thickened and smooth. Off the heat, add the Gruyére, Cheddar, 1 tbsp salt, pepper, and nutmeg. Add the cooked macaroni and stir well. Pour into a 3 quart baking dish.
Slice the tomatoes and arrange on top. Melt the remaining 2 tbsps butter, combine them with fresh bread crumbs, and sprinkle on top. Bake for 30 to 35 minutes or until the sauce is bubbly and the macaroni is browned on top.
To make ahead, put the macaroni and cheese in the baking dish, cover, and refrigerate until ready to bake. Put the tomatoes and bread crumbs on top and bake for about 40 to 45 minutes.