All-Purpose Breakfast Casserole

For the vegetarian toppings:
Heat the olive oil over medium heat in a large skillet. Add the chopped onions and sauté until softened, then add in the sliced mushrooms and chopped garlic. Stir until evenly combined and sauté until the mushrooms have softened and caramelized. Break up the drained spinach and stir it into the mushroom mixture until evenly distributed. Remove from heat and set aside until ready to use.

For the casserole assembly:
Spray a 9×13 baking dish with cooking spray. Scatter the bread cubes along the bottom of the pan. Cover the bread with desired toppings according to the vegetarian or the sausage and cheese version ingredients lists above.

In a large bowl combine the eggs, milk, dry mustard, salt, pepper and hot sauce. Whisk until evenly combined. Pour over the casserole dish. Cover and refrigerate overnight.

The next morning, preheat the oven to 350 F. Pull the casserole from the refrigerator and set it on the counter to let it come to room temperature. Top with desired cheese (listed above). Bake for 50-60 minutes, or until the eggs are set and the cheese is melted.