Step 1

Prepare a 9 by 13 inch casserole dish by buttering the pan. Add cubed sourdough bread to the buttered pan.

Step 2

Cook 1 lb of breakfast sausage in a skillet over medium heat until browned and cooked all the way through. Reserve some of the grease to use in cooking the vegetables and pour cooked breakfast sausage evenly over the cubed sourdough bread.

Step 3

While the sausage is cooking, prepare the vegetables by slicing and dicing peppers, onion and garlic. Pour a little of the grease from the sausage into the same frying pan and sauté peppers and onions over medium-low heat for about 5-10 minutes until softened. Add the garlic and a pinch of salt and pepper to the pan and sauté another few minutes until fragrant. Pour the vegetables on top of the sausage in the casserole dish.

Step 4

Shred the Gruyere and Parmesan cheeses and sprinkle on top of the vegetables, covering the entire casserole dish.

Step 5

To a medium-sized bowl, whisk together eggs, milk, mustard powder, salt and pepper until combined. Pour evenly over the top of the casserole. Cover with aluminium foil and stick in the refrigerator for one hour or overnight (12-16 hours).

Step 6

Before baking the breakfast casserole, pre-heat the oven to 350ºF. Place the casserole in the oven and bake for 20 minutes with the aluminum foil covering the casserole. After 20 minutes, take the cover off the casserole and bake for another 30-35 minutes until puffed up, browned and baked all the way through. Let cool for about 5 minutes and serve. Enjoy!