Ingredient:

• 2 red apples, cored (such as Fuji, Gala, or Pink Lady)
• 1 pound ground beef
• 1/4 cup fine dry bread crumbs
• 5 teaspoons chili crisp, divided, plus more for serving
• 1/2 teaspoon salt
• 2 (1⁄3-inch) slices red onion
• 4 hamburger buns
• 1/4 cup mayonnaise