Meatballs: Add milk to breadcrumbs and allow to soak for 5 minutes. Mix breadcrumbs, ground beef, egg, 1/2 cup water, grated onion, salt and pepper. The meatballs will be a little loose - that is OK because that will ensure tender meatballs. Form into 1-1/2 inch meatballs - place on foil-lined baking sheet sprayed with non-stick spray. Bake meatballs at 350 for 30 minutes. Remove from oven and set aside.
Melt butter in saucepan - add minced onion and cook on medium heat until onion softened. Add drained mushrooms to sauteed onion and cook for 3 minutes. Add 4 cups of water, 4 pkgs of mushroom gravy mix and cook until thickened. If gravy is not as thick as you would like, mix 1/4 cup of flour with 1/2 cup of water and whisk until smooth - add to gravy in small amounts to thicken to your preference. Add 3 shakes of worcestershire sauce to gravy.
Add meatballs to gravy and set burner to low to keep warm. Cook egg noodles according to package directions and drain. Add 2 tablespoons of butter to noodles and toss. Mix sour cream into gravy and meatballs and stir gently. Ladle meatballs and gravy over cooked egg noodles - garnish with fresh, chopped parsley if desired.