With small knife, make horizontal slit in chicken breasts to create pockets, being careful not to cut all the way through.
Sandwich 1 cheese slice between 2 basil leaves; stuff into pockets. Secure with toothpicks. Sprinkle chicken with 1/8 teaspoon of the salt and pepper.
Heat large skillet over medium-high heat until hot. Add oil; heat until hot Cook chicken 5 minutes; turn.
Scatter tomatoes over chicken; sprinkle with remaining 1/8 teaspoon salt. Reduce heat to medium-low. Cook, covered, 4 to 5 minutes or until chicken is no longer pink in center. Sprinkle chicken with torn basil.