Combine mayonnaise and mustard in a small bowl. Spread about 1 teaspoon mayonnaise mixture over 1 side of each bread slice. Top each of 4 bread slices with 1 turkey slice, 1 ham slice, 1 cheese slice, and 2 tomato slices. Top with remaining bread slices.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add sandwiches to pan; cook 3 minutes or until lightly browned. Coat tops of sandwiches with cooking spray. Turn sandwiches over; cook 2 minutes or until cheese melts.
Young Chefs can:
Stir together mayonnaise and mustard
Count out slices of bread, turkey, ham, tomato, and cheese