Preheat your oven to 375°F (190°C).
Unroll the crescent roll dough on a clean surface.
Separate the dough into triangles along the perforated lines.
Place a slice of ham on each triangle.
Add a slice of cheese on top of the ham.
If using, spread a little Dijon mustard over the cheese.
Starting from the wide end, roll the triangle towards the point.
Place the rolls on a baking sheet lined with parchment paper.
Beat the egg and brush it over the tops of the rolls.
Bake for 12-15 minutes or until golden brown.