How to Make It
Stir together mayonnaise and mustard in a small bowl; set aside. Stack iceberg lettuce leaves on a large piece of parchment paper. Shingle leaves from left to right while stacking to create an 8- x 9-inch rectangle, with 9-inch side facing you.
Spread mayonnaise mixture on lower half of iceberg leaves, making sure to spread all the way to the edges. Place chicken in center of mayonnaise mixture. Top with tomato slices, sprouts, cucumber slices, onion slices, and cheese slice.
Using parchment as a guide and starting with side closest to you, roll into a tight log. Once completely rolled, roll remainder of parchment around lettuce. Cut in half, and serve.