Set to 400°F (200°C) and line a baking sheet with parchment paper.
Roll out the puff pastry on a lightly floured surface and spread a thin layer of mustard evenly over it.
Layer the slices of ham evenly across the pastry, then sprinkle the shredded cheese on top.
Roll the pastry tightly into a log, wrap it in plastic wrap, and refrigerate for 10–15 minutes to firm up.
Cut the chilled roll into ½-inch slices and place them on the prepared baking sheet. Brush the tops with egg wash and sprinkle with sesame or poppy seeds, if using.
Bake for 12–15 minutes or until golden brown and puffed.
Garnish with chopped parsley and serve immediately.
