Start and cook pasta accordingly. Preheat oven at 350 °F.
Blend together all meatball ingredients until mixture is uniform. Form tablespoon sized meatballs and place them on a cookie sheet or parchment paper.
Heat up a seasoned or oiled skillet that is safe to go into the oven. Brown all meatballs over medium to high heat on two sides. After turning meatballs and browning slightly, place skillet in oven and bake for 15-30 minutes; depending on the size of your meatballs.
In another nonstick pot melt 2 tbsp butter and saute mushrooms and onions over medium to high heat.
Add and melt remaining butter. Whisk in flour to form a paste mixture.
Add in beef broth and bring to a light boil. Cook gravy until mixture thickens. If it is too thick then add a little more beef broth.
Finally stir in sour cream and bring back to a slight boil. Serve hot meatballs and sour cream gravy over hot pasta and enjoy.