1 to 1 1/2 lb. skinned boneless chicken breasts
1/4 c. vegetable oil
1/4 c. fresh lemon juice
1/2 tsp. fresh ground pepper
3 tbsp. tarragon vinegar
2 tbsp. dry white wine
1 tsp. dried tarragon
4 tbsp. butter
1 tbsp. Dijon mustard

Mix oil, lemon juice, and pepper in shallow dish. Add chicken and marinate for at least 30 minutes. Put vinegar, wine, and tarragon in small pan. Boil until reduced to about 2 tablespoons. Reduce heat to low. Add butter and mustard, stir until butter melts. Keep warm. Drain chicken well. Grill or broil over medium heat, turning once and basting frequently with mustard sauce, until just cooked through, about 5 minutes a side. Be careful not to over cook.