Mirliton and Hot Sausage Casserole

Name: Mirliton and Hot Sausage Casserole
Ingredients: 1 cup finely chopped bell pepper; 1 pound hot Italian sausage, removed from the casings and broken into bite size pieces; 1 tablespoon freshly minced basil leaves; 1/2 cup chicken stock, if needed; 1/2 cup cubed fontina or Swiss; 1/2 cup cubed mozzarella; 1/2 cup freshly chopped green onions; 1/4 cup freshly minced parsley leaves; 2 1/2 teaspoons salt; 2 cups cubed day old French bread; 2 large eggs; 2 tablespoons heavy cream; 2 tablespoons minced garlic; 2 teaspoons freshly minced thyme leaves; 3 cups finely chopped yellow onions; 3 tablespoons dry bread crumbs; 3 tablespoons finely grated Pecorino Romano; 3 tablespoons olive oil, divided; 3 tablespoons unsalted butter; Freshly ground black pepper