Pork Medallions with Tarragon Mustard Sauce

4 1-1/2" thick pork tenderloin medallions
2 tbsp. butter
1/2 cup beef stock
3/4 tsp. tarragon
1/2 cup heavy cream
1 tbsp. Dijon mustard
Salt and pepper

Melt butter in skillet over medium high heat.  Add pork and saute until cooked through, 5-8 minutes on each side.  Transfer to heated dish, cover and keep warm.  Pour off fat.  Add broth and tarragon to skillet and cook over high heat until reduced to 1/4 cup, about 10 minutes.  Stir in cream and cook until thickened, 3-4 minutes.  Whisk in mustard.  Season with salt and pepper.  Spoon sauce over medallions and serve.