Combine the ground chicken, barbecue sauce, minced garlic, salt, and pepper, stirring just until combined. Then, gently form the ground chicken into 4 patties.
Dredge each of the patties in flour, shaking of any excess. Then, dip the patties into the egg before coating them in bread crumbs.
Heat the oil in a large skillet. When it shimmers, add the patties and cook them until the internal temperature reaches 165 degrees F on an instant-read thermometer, about 4 minutes per side.
Spread mayonnaise onto the toasted buns and then place a patty on each bun. Top the patties with parsley, red onion, and tomato, to taste.