From John Ferguson's recipe file.

Sauté bacon and onions over medium heat until bacon is crisp.
Using slotted spoon, transfer bacon-onion mixture to a small bowl.
Pour off drippings from skillet.
Remove from heat.
Add wine and vinegar to skillet.
Return to heat and bring to a boil, scraping up any browned bits.
Boil until liquid is reduced to 1/4 cup.
Add cream and bacon-onion mixture and simmer until reduced to a sauce consistency, stirring occasionally.
Season to taste with salt and pepper.