Season chicken breasts with ground black pepper and garlic salt.
Heat olive oil in a medium skillet, and brown the onion and seasoned chicken breasts.
Pour tomatoes and balsamic vinegar over chicken, and season with basil, oregano, rosemary and thyme.
To Freeze: Freeze in freezer safe container.
To Reheat: Heat in a saucepan until sauce is simmering. Simmer for about 15 mins from defrosted or until chicken is cooked through.