Season the chicken breast with salt and black pepper.
Bake the chicken breast in an air fryer or oven at 180°C for 15 minutes.
Slice the rye bread or whole wheat bread in half.
Place the roasted chicken on the bread.
Add your choice of vegetables such as lettuce, tomato, cucumber, and onion.
Drizzle with mustard sauce.
Top with the other half of bread to finish the sandwich.