In a large pan, add in your olive oil. Over medium heat add in your meatballs to brown. Brown your meatballs, about 3 minutes on each side. See my blog notes above on browning techniques. *If you're using homemade raw meatballs, remove them from the pan after browning, they will finish cooking later on in the recipe. *If you're using frozen meatballs, keep them in the pan so that they have enough time to warm all the way through during the remainder of the cooking process.
In your pan add in your butter, mushrooms, onions, garlic, salt and thyme.
As the butter melts, sauté the onions and mushrooms until soft and the garlic and thyme become fragrant. About 1-2 minutes. *If you removed your brown meatballs, using a wooden spoon scrape up the brown meat bits on the bottom of the pan if there are any.
Stir in your red wine vinegar and let it simmer until it evaporates to just about dry, it should take less than 1 minute.
Add in your Worcestershire Sauce, Dijon mustard and pepper. Stir to combine with the rest of the ingredients.
Sprinkle your flour.
Stir around to coat your ingredients. Let cook for about 1 minute.
Pour in your beef stock, add in your meatballs if you took them out and bring it up to a boil.
Add in your noodles and stir so that everything is evenly distributed. Boil for 8-10 minutes until the noodles are cooked. Watch your pan because it may boil over, if it looks like it might, you can turn down the temperature as long as the liquid continues to boil so that the noodles can cook.
After the noodles are cooked, turn off the heat and stir in your sour cream.