In a large skillet on low heat add butter.
While the butter is melting dice up one onion and add to skillet. Turn heat to medium-high.
Quarter the mushrooms and add to skillet. You want to cook the onions and mushrooms until all of the liquid from the mushrooms is dissolved.
Once the liquid is dissolved add the milk, heavy cream, cream of mushroom soup, and beef bouillion cubes. You will need to crush and stir the bouillion cubes about 2-3 minutes into cooking the sauce.
Once the sauce starts to bubble turn it off. The meatballs should be just about done if not already.
Take the meatballs and add them to the sauce and mix.
Serve over wide egg noodles.