Use a sharp knife to cut cabbage, onion, and sausage and place in a 5-quart crockpot. Add minced garlic, salt and pepper to crockpot, stir to combine.
Cut butter into small pieces and put on top of cabbage mixture. Cover and cook 5-6 hours on low.
Just before serving, cook noodles according to package instructions until a bit more than al dente. Drain from water, gently fold noodles into cabbage mixture. Adjust seasonings to taste.