Add the sausage and onion powder into a large skillet and fry, breaking up all the chunks. Season this with salt and pepper cooking until the sausage is browned. Preheat the oven to 350°F and grease a 7×11-inch baking dish with nonstick spray.
In a separate bowl, break the eggs. Whisk together with milk and brown sugar. Pour this mixture over the top of the cheese. In the greased skillet, melt the butter over medium heat. Stir in the flour and allow this to cook for at least 3 minutes.
Whisk in the salt, pepper, thyme, and milk (slowly). Heat this on medium heat until thickened. Pour the gravy over the casserole. Bake for 35 to 40 minutes. If biscuits and eggs are not fully cooked, continue baking for 5 more minutes at a time.
Simply wrap the baking dish with leftovers tightly with aluminum foil or plastic wrap. Then store it in the refrigerator for up to 3 days. The leftovers can also be stored in the freezer for up to 3 months.