1. Preheat oven to 375 degrees. Butter four 8-ounce ramekins or custard cups. Set a kettle of water to boil.

2. Meanwhile, in a medium skillet, heat 2 tablespoons butter over medium-low. Add bread; cook, tossing occasionally, until lightly browned, 6 to 8 minutes. Season with salt and pepper, and transfer to a bowl; reserve skillet.

3. Melt remaining tablespoon butter in skillet over medium. Add onion; season with salt and pepper. Cook, stirring occasionally, until softened, 3 to 5 minutes.

4. Dividing evenly, spoon onion into ramekins, and top with croutons. Gently break 1 egg into each ramekin (keeping the yolk intact, see below). Top each egg with 1 tablespoon cream, and season with salt and pepper. Place ramekins in an 8-inch square baking dish, and pour enough boiling water to come halfway up side of ramekins. Bake until whites are set, 15 to 18 minutes.

5. Carefully remove ramekins from water bath, and serve immediately.