Pork Medallions with Mustard Cream Sauce

I have had my eye on this recipe since my latest Paula (Jan./Feb.) came in the mail.  I finally had the opportunity to make it last night for dinner.  DELICIOUS!!  I know you are never supposed to make changes to a recipe until after you try it the original way the first time, but I am notorious for not having a specific ingredient.  So here is the version I made.

1 pork tenderloin, trimmed and cut into 1-inch thick slices
salt
pepper
1/2 stick butter, divided into (2) 2 Tbsp. pieces
1 small onion, thinly sliced
1/2 c. white wine
1-1/2 c. heavy cream
1 Tbsp. coarse grained mustard

Sprinkle salt and pepper to taste on both sides of the tenderloin.  In a large skillet, melt 2 Tbsp. butter.  Add pork and cook on both sides.  Remove from skillet and keep warm.

Melt remaining 2 Tbsp. butter in skillet and add onion, stirring constantly, for 2 minutes.  Slowly add wine, and cook, stirring to loosen brown bits from the bottom, until the wine is reduced by half.  Add cream, and simmer for 4-5 minutes or until sauce is thickened.  Stir in mustard.  Serve immediately over pork medallions.

**Don't make this sauce ahead of time and plan to reheat to serve.  It separates.