Preheat the oven to 450 degrees. Place a piece of parchment paper on a sheet pan.
Lay one sheet of puff pastry on a floured board and lightly roll into a 10-inch square.
Place it on the sheet pan and brush the pastry with all the mustard, leaving a 1-inch border.
Lay soppressata overlapping on the mustard.
Sprinkle on the cheese.
Brush the border with the egg wash.
Lightly roll the second piece of puff pastry into a 10-inch square and lay on top of the first square Brush the top with the egg wash.
Cut a few slits and chill in fridge. I usually make ahead of party and chill 1-2 hours.
Trim all edges before baking.
Bake 20 to 25 minutes until puffed and brown.