Preheat oven to 375 degrees F (190 degrees C). Lightly grease a 9x13 inch square baking dish.
Place sausage in a large, deep skillet. Cook over medium-high heat until evenly brown. Drain, crumble, and set aside.
In the prepared baking dish, stir together the shredded potatoes and butter. Line the bottom and sides of the baking dish with the mixture. Bake for approx. 30 minutes while you brown the sausage. In a bowl, mix the sausage, Cheddar cheese, onion, cottage cheese, and eggs. Pour over the potato mixture.
Bake 1 hour in the preheated oven, or until a toothpick inserted into center of the casserole comes out clean. Let cool for 5 minutes before serving.