How to Make It
Melt butter in a medium skillet over medium-low. Add onions and bay leaf, and cook, stirring occasionally, until deeply caramelized, about 40 minutes.
Preheat oven to 375°F. Increase heat to medium, and deglaze skillet with beef stock and wine. Add thyme, salt, pepper, and garlic; cook, stirring occasionallly, until liquid is reduced to 1/4 cup, about 5 minutes. Stir in sherry. Remove from heat, and stir in beef, rice, and 1 1/2 cups of the cheese.
Slice tops off bell peppers, and reserve for another use. Remove seeds and membranes. Divide onion mixture evenly among peppers. Place stuffed peppers in a baking dish; cover and bake in preheated oven until peppers have softened, 45 to 50 minutes. While peppers are baking, toss together bread, oil, and remaining 1/2 cup cheese in a bowl.
Reduce oven temperature to 350°F. Uncover peppers, and top each evenly with bread mixture. Return to oven, and bake until tops are bubbly and lightly golden, about 10 minutes.