Preheat oven to 450°F Place a piece of parchment paper on a sheet pan.
Lay one sheet of pastry on a floured board and roll into a 10 inch square. Place on a sheet pan and brush with the mustard, leaving a 1 inch border. Arrange soppressata in overlapping layers on the mustard and sprinkle with cheese, also avoiding the border. Brush border with egg wash.
Lightly roll second piece of pastry into a 10 inch square. Lay directly on top of first square, lining up the edges. Brush top with egg wash and cut 3 large slit for steam to escape. Chill for 15 minutes.
When pastry is cold trim edges with a sharp knife to make a clean edge. Bake in center of oven for 20 to 25 minutes, rotating once while baking, ubtil puffed and brown. Allow to cool for a few minutes before cutting into serving sizes.