For the homemade casserole, boil the potatoes. Bring the pasta water with salt also to a boil and let the pasta steep in it. In the meantime, fry the onions and minced meat (or sausage) and place in a casserole dish. Mix the soup with the remaining pasta water (it will be very creamy because the water already contains starch). Use a little less water than for a normal soup. Then mix all the ingredients in the casserole dish and sprinkle with grated cheese. Bake the casserole homemade at 200°C until the cheese is nice and crispy.