Unfold Puff Pastry. Spread Mustard Over Pastry To Within 1/2 In. Of Edges. Sprinkle With Prosciutto And Cheese. Roll Up One Side To The Middle Of The Dough; Roll Up The Other Side So The Two Rolls Meet In The Center. Using A Serrated Knife, Cut Into 1/2-In. Slices. Place On Greased Baking Sheets. Bake At 400