Preheat the oven to 375 F. Cook sausage in a large, deep skillet over medium-high heat until evenly browned. Drain, crumble and set aside. Lightly grease a 9 x 13-inch baking dish. In the prepared baking dish, stir together the shredded potatoes and butter. Line the bottom and sides of the baking dish with the mixture. In a bowl, mix together sausage, Cheddar cheese, onion, cottage cheese and eggs. Pour over the potato mixture. Bake 1 hour, or until the casseroles reaches a safe internal temperature of 160 F as measured with a food thermometer. Let cool for 5 minutes before serving. Refrigerate any leftovers.