Slice the chicken breast thinly.
Julienne the carrots to make carrot râpées (French carrot salad).
Cut the baguette (or whole wheat bread) in half.
Spread mustard sauce on the bread.
Layer chicken breast, jambon (low-sodium ham), and carrot râpées in order.
Add leafy greens such as lettuce or arugula.
Cover with the other half of the bread to finish the sandwich.