Preheat your oven to 350°F.Lay out your puff pastry squares and spread some mustard, diagonally from one corner to the opposite corner.Roll up your cold cuts and place on top of the mustard. Then roll up tightly, gently pulling the corner and tucking underneath so it doesn't unroll while baking.Brush with duck sauce and sprinkle sesame seeds if you wish.Bake on a parchment lined baking sheet until golden brown, about 30 minutes.