Pound chicken with a meat mallet to 1/4 inch thickness; sprinkle with salt and pepper. In a large skillet, cook chicken in oil over medium heat for 4-5 minutes on each side or until no longer pink. Remove and keep warm
In the same skillet, cook and stir onion in 1 tablespoon butter over medium high heat for 1-2 minutes or until tender. Add garlic; cook 1 minute longer. Add the cherries, vinegar, wine and stock, stirring to loosen browned bits from pan. Bring to a boil; cook until liquid is reduced by half and cherries are plump - about 6 minutes. Stir in mustard. Serve over rice with sauce.