Defrost puff pastry sheets. Flatten. Smear mustard on top of puff pastry sheets.
Place contrasting alternating slices of deli meat on top of mustard. Fold pastry sheets to the middle to close. With a pastry brush, spread egg on top of puff pastry. Sprinkle sesame seeds on top. Create a series of slits to vent.
Bake on cookie sheets at 350 degrees for about 45 minutes or until golden brown.