Preheat oven to 350°F and grease a 9×13-inch casserole dish.
Brown the sausage in a skillet. Remove 1 cup and set aside.
1 lb breakfast sausage
Add butter to remaining sausage, then stir in flour and cook for 2–3 minutes.
1 tbsp butter, 3 tbsp all-purpose flour
Gradually whisk in milk and cook until thickened into gravy. Season and set aside.
2 cups milk, salt and pepper
In a bowl, whisk together flour, baking powder, baking soda, and salt.
2 cups all-purpose flour, 2 tsp baking powder, 1/4 tsp baking soda, 1/4 tsp kosher salt
Add frozen shredded butter and mix to coat. Stir in buttermilk until just combined.
1/2 cup butter, 1 cup buttermilk
In another bowl, whisk eggs, milk, salt, and pepper. Stir in cheese, green onions, and reserved sausage.
6 eggs, 1/2 cup milk, 2 cup sharp cheddar cheese, 1/3 cup green onion, 1/4 tsp kosher salt, 1/4 tsp black pepper
Pour egg mixture into prepared dish.
Portion biscuit dough into 12 pieces and place on top.
Spoon half the gravy over biscuits.
Top with remaining cheese and bake 25–30 minutes until golden and set.
Rest 10–15 minutes before serving. Serve with remaining gravy.