Creamy Tarragon Chicken

6 boneless skinless chicken breasts
2 T. butter
Salt & pepper
½ c. chopped onion
1 clove garlic, minced
1 T. tarragon
¼ c. flour
1 ½ c. cold water
1 c. sliced mushrooms
1 c. cream

Melt butter in skillet. Add chicken breasts. Sprinkle with salt and pepper and cook on medium heat about 5 minutes on each side. Sprinkle onion, garlic and tarragon over chicken and cook for another 5 minutes. Whisk together flour and water until smooth. Pour over chicken. Add mushrooms and cook for about 10 minutes until mixture thickens. Stir in cream and cook until misture just starts to bubble. Serve with mashed potatoes.