In a very large skillet, cook sausage on medium high heat, breaking up the meat and browning it. Once cooked through, drain and layer onto the bottom of a 9x13 inch baking pan. Evenly sprinkle 2 cups of the cheese over cooked sausage.
In a large bowl, hand-whisk together the milk, eggs, pepper, onion powder, and salt. Once mixed, pour evenly over the cheese and sausage in baking dish. Layer top with frozen hashbrown patties.
When ready to bake, set oven to 350F with rack on lower middle position. Once oven reaches 350F, place casserole in oven for about 35 minutes. Top with additional ½ cup cheese, cooked/crumbled bacon, and bake another 5-10 minutes or until sides are bubbling and top is golden brown. Garnish with chopped parsley, let rest at room temp 10 minutes, and serve.