Lightly mix 6 ounces ground beef chuck with a big pinch of kosher salt. Form into a ball, then into a 3/4-inch-thick patty; make an indentation in the center. Mix 3 tablespoons hoisin sauce and 1 tablespoon each soy sauce, rice wine and honey; brush on the patty and broil 4 minutes per side, brushing with more sauce.
Brush a bun top with a beaten egg white; sprinkle with Japanese rice seasoning and bake at 350 degrees, about 5 minutes. Serve burger on Asian-spiced bun with broiled scallions and mayonnaise.