Steps
1. In a bowl, combine the mayonnaise, Dijon mustard, salt, and pepper to create a creamy dressing.
2. Lay the tortilla flat on a clean surface.
3. Spread the dressing evenly over the tortilla.
4. Place the shredded chicken in the center of the tortilla.
5. Top with shredded lettuce, diced tomatoes, and sliced avocado if using.
6. Fold in the sides of the tortilla, then roll it up tightly from the bottom to the top.
7. Cut in half and serve immediately.