Pasta and Lamb Casserole Pastitsio

Name: Pasta and Lamb Casserole (Pastitsio)
Ingredients: 2 medium onions, finely chopped; 2 tablespoons olive oil; 2 large garlic cloves, finely chopped; 2 pounds ground lamb; 1 (28-ounces) can whole tomatoes in juice; 1 (15-ounces) can whole tomatoes in juice; 4 thyme sprigs; 1 1/4 teaspoons ground cinnamon; 1 1/4 teaspoons ground allspice; 1/2 teaspoon grated nutmeg; 1/4 teaspoon ground cloves; 7 tablespoons unsalted butter; 6 tablespoons all-purpose flour; 7 cups whole milk; 3/4 teaspoon grated nutmeg; 1 cup grated Parmigiano-Reggiano or kefalotyri cheese (2 ounces); 5 large egg yolks; 2 pounds ziti; 1 3/4 cups coarse fresh bread crumbs (from 4 slices firm white sandwich bread); 1/4 cup grated Parmigiano-Reggiano or kefalotyri cheese