Spray crock pot and evenly spread hash browns at the bottom.
Crack 12 eggs in a large bowl.
Mix well (and slowly) using a whisk.
Add the milk.
Go ahead and sprinkle in the ground mustard. This might sound like a weird ingredient, but I've come to love (and use) this in most of my recipes.
Add plenty of salt.... and lots of fresh pepper. Mix well and set aside.
Cook the sausage on high heat, drain and set aside.
Add sausage on top of hash browns.
Is this enough cheese? Maybe? Probably. Throw the whole big bag in there.
Mix it up well. Or good, depending on where you're from.
Pour the egg mixture over everything in the crock pot. Using a wood spoon, even everything out so it's spread evenly.
Turn the crock pot on low for 6-8 hours.
Replacing frozen hash browns with grated raw russet potatoes dramatically alters the moisture level, requiring an extra fifteen minutes of draining in a fine-mesh strainer to prevent a watery bottom layer. Slow cookers operate through prolonged, gentle heat transfer, meaning raw ingredients like pork sausage must be fully browned in a skillet beforehand to render excess fat and develop Maillard compounds that would otherwise never form at ceramic vessel temperatures. When whisking the dozen eggs, incorporate the ground mustard and dairy thoroughly before pouring, because lipids act as an emulsifier that keeps the proteins from separating into a rubbery curd during the six to eight hour cooking window on low heat.
Managing Thermal Mass in Ceramic Cookers
Ceramic slow cooker inserts retain heat long after the heating element turns off, meaning dishes continue to cook for up to twenty minutes after unplugging the appliance. Leaving the lid slightly ajar during the final thirty minutes allows trapped steam to escape, which concentrates the dairy and prevents the cheese from breaking into an oily pool atop the casserole.
Common Pitfalls and Moisture Control
Overcooking ruins egg casseroles quickly by driving out moisture and causing the sulfur compounds to concentrate into an unpleasant metallic taste. Sourdough bread chunks absorb free liquid efficiently if added during assembly, while watery additions like fresh salsa require prior reduction in a hot pan to maintain structural integrity.