Preheat oven to 350o F. Grease a muffin tin with cooking spray.
Begin melting butter in a large skillet over medium-high heat. Once butter is melted and pan is hot, add frozen hash browns. Sauté until golden brown and crispy. About 10 minutes. Remove from pan and set aside.
Add sausage to the same skillet. Break up the sausage and cook until brown. About 5 minutes. Remove from pan and set aside.
In a medium mixing bowl, whisk eggs and milk until combined. Add salt and pepper to taste.
Evenly distribute cooked hash browns into each muffin cup.
Evenly distribute the sausage into each muffin cup.
Pour egg mixture over the hash browns and sausage.
Sprinkle each muffin cup with shredded cheddar cheese.
Bake in preheated oven for 20 minutes, or until the cheese becomes golden brown and bubbly.
Allow the egg cups to cool in the muffin tin for at least 5 minutes before removing.
Enjoy hot or cool to room temperature and freeze for future breakfasts.