1. Preheat grill to 350° to 400° (medium-high). Gently combine ground chuck, sausage, and next 6 ingredients. Shape mixture into 4 (4-inch) patties.
2. Grill patties, covered with grill lid, over 350° to 400° (medium-high) heat 4 to 5 minutes on each side or until beef is no longer pink in center.
3. Grill hamburger buns, cut sides down, 1 to 2 minutes or until lightly toasted. Serve burgers on buns with Cajun Mustard and desired toppings.