Layer half the bread, 1 cup of cheese, and half the bacon or sausage, and then repeat with the rest of the bread/cheese/meat. This part isn't rocket science. You really can't mess it up.
Beat the eggs and add the milk, mustard powder and salt if using. Mix well.
Pour the liquid evenly over the bread, cheese and meat. Next, drizzle the butter evenly over the top.
Cover with parchment paper and then foil. Refridgerate for 8 hours or overnight. Next morning pull it out and let it sit for 1 hour on the counter. Place in the oven and turn the temperature on at 350F.
Bake for 30 minutes, and remove the foil and parchment paper. Bake an additional 30 minutes. Let sit for at least 15 minutes before serving.
Serve with salsa, hot sauce and/or sour cream.