In large mixing bowl, blend ground beef and sausage; divide into eight patties. On grill over medium heat, cook burgers on each side until no longer pink in center and internal temperature reaches 160 degrees, about 15 minutes.
Heat macaroni and cheese according to package instructions.
Place patties on buns and top each with 1/4 cup macaroni and cheese, 1/2 teaspoon Buffalo sauce, and sprinkle with blue cheese, if desired.
For Barbecue Mac & Cheese Burgers instead: Top each patty with 1/4 cup macaroni and cheese, 2 teaspoons barbecue sauce, and French-fried onion straws.