In a very large bowl, combine hoisin sauce, finely chopped onion, five-spice powder, and crushed red pepper. Add beef and pork; mix well. Shape into six 1/2-inch-thick patties.

For a charcoal grill, place patties, pineapple, and red onion on the rack of an uncovered grill directly over medium coals. Grill pineapple and onion for 4 to 6 minutes or until lightly browned, turning once. Grill patties for 10 to 13 minutes or until an instant-read thermometer inserted into side of each patty registers 160 degrees F, turning once halfway through grilling. (For a gas grill, preheat grill. Reduce heat to medium. Place patties, pineapple, and red onion on grill rack over heat. Cover and grill as above.)

Halve pea pods lengthwise. Place pineapple on bun bottoms. Top with patties, red onion, pea pods, and bun tops.