First Step: Prepare and Preheat: Preheat your oven to 350°F (175°C) and grease a 9 x 13-inch baking dish with 1 tablespoon of unsalted butter. Remove crusts from bread slices and cut into 1-inch cubes or tear six slices into rough pieces as an alternative. This sets the stage for even baking and flavor infusion.

Second Step: Cook Sausage and Onions: In a large nonstick skillet over medium-high heat, melt the remaining 1 tablespoon of butter. Add the sausage (casings removed) and cook, breaking it into small clumps until browned, about 10 minutes. Transfer the cooked sausage to a large mixing bowl, leaving the fat in the skillet. Reduce heat to medium, add the chopped onion, and sauté until soft and translucent, roughly 5 minutes. Stir the onions into the bowl with sausage.

Third Step: Assemble Bread, Cheese, and Parsley: Add the cubed or torn bread, grated sharp cheddar cheese, and optional fresh parsley to the bowl containing sausage and onions. Mix gently to combine evenly. Spread this mixture into the prepared baking dish, creating a uniform layer that will soak up the custard mixture.

Fourth Step: Whisk Eggs and Milk: In a medium bowl, whisk together six large eggs, two cups of half-and-half (or milk/cream for richer texture), a scant teaspoon of salt, and ¼ teaspoon freshly ground black pepper until well blended. This egg mixture forms the custard that binds the casserole.

Fifth Step: Combine and Refrigerate: Pour the egg mixture evenly over the bread, sausage, and cheese mixture in the baking dish. Cover tightly with plastic wrap and refrigerate for at least 2 hours or overnight. This refrigeration step allows the bread to absorb the custard fully and flavors to meld, making the casserole more flavorful and cohesive.

Sixth Step: Bake the Casserole: Remove the plastic wrap and place the casserole in the preheated oven with the rack in the center position. Bake uncovered for 45 to 60 minutes, or until puffed, golden brown, and the eggs are fully set. If baking immediately from the refrigerator, start checking doneness at 45 minutes to avoid overcooking.

Final Step: Serve and Enjoy: Let the casserole cool slightly before slicing. For presentation and extra flavor, garnish with fresh parsley or a side of mixed greens. This satisfying bread casserole makes a hearty breakfast or brunch centerpiece, adaptable to many palates.