Preheat oven to 350 degrees. Cut chicken into pieces about 1x2 inches. Mix soy sauce, maple syrup, sherry, ginger and chinese five spice together. Add chicken and marinate 20 minutes, turning once.
Meanwhile, place sesame seeds on a baking tray and toast in oven for 10 minutes or until slightly brown. Drain chicken, reserving marinade. Dredge chicken in flour seasoned with a little salt and pepper. Shake off any excess.
Heat oil in a non-stick skillet. Add chicken and brown, about 1 minute per side. Spoon marinade over chicken. Reduce heat and saute another minute, or until chicken is cooked through. Remove from heat and roll chicken in sesame seeds.
Wash and dry lettuce leaves. Line a serving plate with leaves, and spoon chicken on top. Cut tomato into wedges and use to garnish plate.