Preheat the oven to 400°F and line a baking sheet with parchment paper.
Roll out the puff pastry slightly on a floured surface and cut it into 4 equal squares.
Mix cream cheese and Dijon mustard in a bowl.
Spread a thin layer of the cream cheese mixture in the center of each pastry square. Arrange 3-4 asparagus spears diagonally across the pastry. Fold two opposite corners of the pastry over the asparagus and press gently to seal. Brush the pastry with egg wash and sprinkle with sesame seeds and Parmesan (if using).
Place on the prepared baking sheet and bake for 15-20 minutes, or until golden brown and crispy.
Serve warm & enjoy!