Leave the steak or roast drippings in the cooking pan.
Add the garlic and onions to it over medium heat.
Stir until the onion is tender (about 1-2 minutes).
Stir in the red wine, beef stock, and vinegar
Bring to a rapid simmer (do not change the heat setting).
Cook five minutes until you see reduction and thickening.
Whisk in 2 Tbs butter.
Salt and pepper to taste.