In a large bowl, mix together the ground beef, onion, breadcrumbs, egg, salt, pepper and nutmeg. Form mixture into 1 1/4 - 1 1/2 inch meatballs and place on a parchment or foil lined baking sheet.
Bake for 22 - 25 minutes. While the meatballs are baking, cook the noodles according to package directions and prepare the sauce.
To make the sauce, melt the butter or margarine in a saucepan over medium heat. Whisk in flour to make a roux. Pour in the consommé and continue to whisk until smooth. Stir in Dijon mustard and sour cream. Simmer until thickened (sauce should coat the back of a spoon), and reduce heat to low to keep warm if needed.
Toss cooked pasta and meatballs with sauce and top garnish with chopped fresh parsley before serving.
Recipe by Simply Whisked at http://www.simplywhisked.com/meatball-stroganoff/