IN a large pot, bring 2-3 quarts water to a boil; ADD salt to taste and 8-12 ounces egg noodles; RETURN to a boil.
WHILE noodles are cooking, heat 15-25 frozen cooked small meatballs in a microwave at 100% power for one minute.
INTO a large heavy-bottomed saucepan over medium-low heat, add 1/3 cup butter until melted; ADD 1/3 cup flour; COOK just until just bubbly (but not browned).
WHEN noodles are tender yet firm, drain; RETURN drained noodles to pot over low heat; ADD 1 tablespoon butter and 1/2 tablespoon of the minced fresh parsley; KEEP noodles warmed over lowest heat (refresh noodle moistness by adding a little water if needed).
OPEN both cans of beef broth; QUICKLY whisk in beef broth into butter and flour roux until smooth; STIR in the remaining minced parsley, lemon juice, Worcestershire sauce, seasonings and freshly ground pepper to taste; ADD the mushrooms and meatballs; BRING mixture to a boil while stirring; REDUCE heat to medium-low until fully thickened.
STIR in 1 cup sour cream; KEEP sauce warmed until serving, stirring as needed.
FOR SAUCE AND MEATBALLS SERVED OVER NOODLES: Arrange warm buttered egg noodles on serving plates. Ladle warm sauce and meatballs over noodles.
FOR NOODLES MIXED WITH SAUCE AND MEATBALLS: Gently fold sauce with prepared noodles until well-blended.
GARNISH each serving with a light dusting of paprika (or a pinch of dried dill), and a fresh parsley sprig if desired.