Place the chicken breasts between 2 sheets of wax paper. Flatten them to 1/4 inch thickness, using a meat mallet or a rolling pin.
Combine the cornstarch, cumin, and garlic salt in a small bowl, stirring well.
Combine the beaten egg and water in a small bowl, stirring well. Place the cornmeal in a shallow plate. Dredge the chicken in the cornstarch mixture; dip in the egg mixture, and then dredge in the cornmeal.
Saute the chicken in oil in a large skillet for 2 minutes on each side or until lightly browned. Transfer the chicken to a 13 x 9 x 2 inch baking pan.
Arrange the avocado slices over the chicken, and sprinkle evenly with the shredded cheese. Bake, uncovered, for 15 minutes or until the cheese melts and the chicken is done. Top with sour cream, green onions, and sweet red pepper. Garnish if desired.