Fold each slice of ham into a rectangle, and place 2 slices ham per pastry on top of the mustard. Top each ham slice with about 2 tablespoons grated cheese. Brush edges with beaten egg, and fold pastry in half, pressing around edges to seal the pastries. Using a fork, lightly crimp the edges.
Repeat with remaining 5 pastries, transferring each to baking sheets as you go.
Lightly brush beaten egg over pastries and sprinkle with Italian seasoning and Parmesan cheese.
Bake each pan of pastries for 15 to 18 minutes, or until golden brown and crispy.