Sprinkle both sides of the chicken generously with Italian Seasoning Mixl.
Heat 2 tablespoons of the olive oil in a large heavy skillet over medium heat. Add the chicken, and cook for several minutes on each side until browned on both sides. Remove the chicken from the skillet onto a plate and set aside.
Add the remaining olive oil, garlic and onion and cook until the onion is just tender, about 2 minutes. Stir in the tomato sauce and olives and return the chicken to the skillet. Cover and cook until the chicken has cooked throughout, about 15 more minutes.