Julienne the carrots thinly.
Mix carrots with salt, sugar, vinegar, and olive oil to make carrot râpé.
Season chicken breast with salt and pepper, grill in a pan, then let cool.
Slice the ciabatta in half, lightly brush with olive oil, and toast.
Spread mustard sauce on the ciabatta, then layer chicken breast, carrot râpé, cheese, and lettuce.
Top with the other half of the bread and cut in half to serve.