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.