In a large skillet over medium high heat, heat olive oil. Add chicken and brown on both sides (about 2-3 minutes per side).
Add butter and mushrooms to skillet and cook for 3-4 minutes.
Add sauce, broth, milk, garlic powder, salt and pepper. Bring to a boil, then reduce heat to medium. Cover and cook for 15-20 minutes (until chicken is no longer pink in the middle).