Cook cleaned, sliced mushrooms in pan with 2 Tbs water over high heat until almost dry.
Remove from pan.

Melt the butter (or bacon grease ) in a pan over medium-high heat.
Add onions and fry until beginning to brown. Add the garlic and cook another minute.
Add mushrooms and cook 4 minutes until well browned.
Add 2 Tbs butter and melt.
Add the flour and cook for about 2 minutes, stirring constantly.

Add the beef broth, vinegar, thyme, sugar, salt and pepper.
Whisk continually until the gravy is thickened.
Cover and simmer on low, stirring occasionally, for 5-10 minutes.
Add salt and pepper to taste.