Cut the chicken breast into pieces and sauté until done and golden with the spices: salt, pepper and curry.
For the sauce, mix the mayonnaise, ketchup and mustard in a bowl, press in the garlic and stir.
Cut the napa cabbage and pickled cucumber into strips, and the tomato into wedges.
Lay the flatbread on the counter, spread half the sauce on the bottom third, and arrange strips of napa cabbage, tomato, carrot, cucumber and chicken on the same section.
Roll up the flatbread. Assemble the second shawarma the same way.
Grill the shawarma on a hot dry grill pan on both sides until golden with nice grill marks.