Wipe out cast-iron skillet; reduce heat to medium. Divide Cheddar among 4 of the bread slices; top each with a patty, caramelized onions, Swiss cheese slice, mayonnaise mixture, and remaining bread.

Chef Carla Hall makes her own crunchy crackers to serve with this cheese spread, a riff on a Southern classic. Carla Hall first won over audiences when she competed on Bravo's Top Chef and Top ...