In a large skillet over medium heat, melt 4 tablespoons of butter. Once melted and bubbling, add 1 cup of diced celery, 1 cup of diced onion, and if using, 1 cup of diced mushrooms. Sauté for about 8-10 minutes until the vegetables are soft and the liquids have evaporated.

Add 1 pound of crumbled pork breakfast sausage to the skillet with the sautéed vegetables. Cook on medium-high heat for about 5-7 minutes until the sausage is browned and cooked through, breaking it apart with a spatula.

In a large casserole dish, combine 6-8 cups of cubed bread dumplings (or French rolls). Spread the bread cubes evenly across the dish, ready for the following mixture.

Carefully pour the sausage and vegetable mixture over the cubes of bread in the casserole dish. Using a spatula, gently mix the ingredients until the bread is well coated with the savory mixture.

In a separate bowl, whisk together 2 large eggs and 1 cup of milk until fully combined. Pour this egg mixture evenly over the bread and meat combination, allowing it to soak for a moment.

Gently pour 2-3 cups of chicken or turkey broth over the entire stuffing mixture. Use a spoon to push down any dry bread pieces into the broth so they can absorb the liquid.

Preheat your oven to 375°F (190°C). Cover the casserole dish with aluminum foil and place it in the oven for 30 minutes. After 30 minutes, remove the foil and bake for an additional 15-20 minutes until the top is golden and crisp.

Once baked, take the stuffing out of the oven and let it rest for 10-15 minutes before serving.