1 c. vinegar
1/2 c. meat broth, butter OR water
1 sm. chopped onion
1 tsp. prepared mustard
1/4 c. to 1 c. ketchup to thicken to desired consistency
"Plenty" of black pepper (+ or - 1 tbsp.)

Combine and let boil for 5 minutes. Simmer uncovered to desired thickness.