Rinse chicken with cold water and pat dry with paper towels. Place between two sheets of plastic wrap and pound to flatten to 1/4-inch thickness.
In resealable plastic bag, combine cornmeal and garlic salt. Add chicken; close bag and toss to coat well. In large nonstick frying pan, heat oil. Cook chicken in hot oil for 2 minutes per side or until lightly browned. Remove chicken from pan and place in shallow baking pan.
Place half of avocado slices over chicken and sprinkle evenly with shredded cheese. Bake at 350° F for 15 minutes or until chicken is done and cheese is melted.
Place each chicken breast on a slice of toast. Top with remaining avocado slices. In small bowl, combine yogurt and pepper; serve with chicken.Servings: 4