1. Cut chicken breast halves into small cubes.
2. In a medium skillet, heat the oil and fry the chicken until cooked through and golden brown (about 8-10 minutes). Season the chicken with salt and pepper. Add the cheese and fry for 1 more minute until it melts.
3. Dice the tomatoes. Warm the tortillas slightly in the microwave to make them more pliable (optional).
4. Line each tortilla with lettuce leaves.
5. Layer tomatoes on top of lettuce.
6. Top the tomatoes with mayonnaise. To squirt mayonnaise, use a pastry bag or a plastic sandwich bag (cut a small hole at one corner of the plastic bag so the mayonnaise can pass through). You can also spread mayonnaise using a spatula.
7. Divide the chicken and cheese mixture evenly among each tortilla.
8. Roll up tightly and enjoy!