Lightly oil a 9x9-inch or 11x7-inch casserole dish. Place your slices of bread in the bottom, cutting in half or tearing up as needed to fill the bottom of the dish in one layer.
Place a medium skillet on the stovetop to warm over medium heat. Add your vegan sausage and cook for 2-3 minutes, stirring to break up and warm through. Remove from the heat and stir in the mustard.
Scoop the sausage out of the pan to layer on top of the bread in the casserole dish. Next, sprinkle the vegan cheese over top.
Whisk together the remaining ingredients (JUST Egg through the pepper), then pour over top of the cheese, sausage and bread. Cover and let rest in the refrigerator overnight.
In the morning, remove the casserole from the refrigerator while you preheat your oven to 350 degrees Fahrenheit. Uncover and bake for about 50 minutes, or until the edges are bubbling and just starting to brown. Remove from the oven and let cool for 10-15 minutes before slicing and serving.
