Turn leftover chicken into a delicious sandwich topped with sauerkraut and mayonnaise.
Turn on broiler, with rack 4 inches from the heat. Thinly slice chicken. Top 4 slices of bread with cheese, then with chicken and sauerkraut.
In a small bowl, stir together mayonnaise and ketchup; spoon over sauerkraut. Place remaining slices of bread on top.
Broil sandwiches, about 2 minutes on each side, until cheese has melted and bread is golden brown. Cut in half, and serve immediately.
