Place the chicken breasts between two sheets of waxed paper. Use a meat mallet to pound the breasts to an even thickness of about 1/2 inch. Remove any excess fat. Slice the chicken into 4 sandwich-sized pieces to fit the buns.

In a shallow bowl, stir together the olive oil, lime juice, and chipotle chili powder to make the marinade.

Place the chicken breasts in the marinade, turning to coat. Cover with plastic wrap and marinate for at least 15 minutes or up to an hour.

Grill the chicken for a couple of minutes on each side until fully cooked through. Place a slice of cheese on each cooked chicken breast and cover the grill for about 30 seconds to melt the cheese.

Place each chicken breast on the bottom buns and top with the avocado, lettuce, mayo, and your favorite toppings. Serve and enjoy!