Pound out the chicken breasts between 2 sheets of plastic wrap until pretty flat. Put the flour, cracked pepper and garlic powder in a Ziploc bag and add the chicken to coat. Remove excess flour.
In a heated non-stick skillet (med-high) add the olive oil and butter. Sauté the chicken until golden brown (about 4-6 minutes on each side). Remove the chicken from the skillet.
If the skillet is too dry, add 1-2 more Tbsp. of olive oil. Sauté the diced onion and minced garlic for 2-3 minutes then add the chicken stock and wine to the skillet. Reduce to about half and then add the mixed vegetables and capers to the skillet and cook for an additional 5 minutes. Return the chicken to the skillet and turn heat to low and cover for another 10 minutes. Serve chicken with pan sauce over white rice or noodles.