Chicken Breast Saute with Vinegar-Tarragon Sauce

1 Tbsp. unsalted butter
1 Tbsp. olive oil
3 Tbsp. minced shallots
4 skinless, boneless chicken breasts
salt and freshly ground pepper
1/4 C. chicken stock
1/2 C. red wine vinegar
2 Tbsp. fresh tarragon or 1 tsp. dried tarragon
1 Tbsp. tomato paste
1/2 tsp. sugar
2 Tbsp fresh parsley

In a nonstick frying pan over medium heat, melt butter with olive oils.  Add shallots and chicken.  Sprinkle with 1/2 tsp. salt and 1/4 tsp pepper.  Cook chicken until browned, 2-3 minutes on each side.

Add water and 1/4 C. of the vinegar and bring to a boil.  Reduce heat to low, cover, and simmer until the chicken is opaque throughout, 5-7 minutes.  Transfer the chicken to a platter, cover loosely with foil and keep warm.

Raise the heat to high and add the tarragon and remaining 1/4 C. of vinegar to the pan.  Boil rapidly to reduce the liquid by about 1/3, about 3 minutes.  Remove from the heat, add the tomato paste and sugar and stir until blended.  Taste and adjust the seasoning.  Pour the sauce over the chicken and sprinkle with minced parsley.  

***Note: Try reducing the amount of vinegar and maybe using a red wine instead of red wine vinegar.  The vinegar in this was too strong