Donatellas Italian Mac Cheese

Name: Donatella's Italian Mac & Cheese
Ingredients: 1 pound elbow macaroni; 3 large egg whites; 1/2 cup unsalted butter + some for greasing bowls; 1/2 onion; 1/3 cup all-purpose flour; 3 1/2 cups whole milk; 1 bay leaf; 1 sprig fresh thyme; 9 whole black peppercorns; 1 kosher salt; 1/4 teaspoon ground nutmeg; 1 carton (8 oz) mascarpone cheese; 6 ounces taleggio/muenster cheese (rind removed); 6 ounces parmigiano-reggiano cheese; 6 ounces pecorino romano; Truffle oil and fresh thyme; Garlic bread crumbs (recipe below); 5 ounces country-style white bread; 2 cloves garlic; 1/2 teaspoon salt; 1/4 teaspoon freshly ground pepper; 2 1/2 tablespoons olive oil