In large skillet saute onions, mushrooms, and garlic until lightly brown; add chicken breast and cook on medium high for 10 minutes or until chicken is done.
Remove chicken and place on a platter. Add white wine and cook until alcohol has burned off, about 2 minutes. Add Worchestershire sauce and sour cream and stir until combined. Pour sauce over chicken, sprinkle with tarragon and serve.
Excellent with biscuits, pasta or rice.