In a large skillet over medium heat, crumble and cook breakfast sausage until browned. Remove from heat and set aside.
Crack eggs into a large bowl. Add heavy cream, salt, onion powder, pepper, and paprika. Whisk to combine. Add thawed hash browns, melted butter, sausage, and cheese. Stir to combine.
Pour into a 9x13 pan and spread into an even layer.
Bake for 45-55 minutes, or until middle of casserole has set and edges are browned. Optionally, garnish with chives before serving.
Make Ahead - This casserole is easy to make ahead the night before, to save time in the morning. Simply prepare your casserole per the instructions, but before baking, cover and refrigerate overnight. Simply preheat your oven in the morning, uncover the casserole, and bake according to the directions.
Freezer Casserole - Bake your casserole and allow to cool completely. Cut into single serving squares, wrap in foil, and store in a freezer bag. Take out a square to thaw in the refrigerator the night before. An individual serving can be reheated in the microwave (times vary based on appliance – use your best judgement) or reheated in a toaster oven (about 15-20 minutes at 350 degrees Fahrenheit).