Heat the oven to 200°C and line a baking tray with parchment paper.
Spread out puff pastry on a clean surface.
Evenly coat pastry with mustard.
Arrange diced ham and grated cheese uniformly over the pastry.
Season with pepper and roll up the pastry starting from the long edge.
Place the roll on the baking tray and pinch the ends securely.
Brush the surface of the strudel with beaten egg.
Bake in the preheated oven for 25-30 minutes until golden brown.
Remove from oven, let cool slightly, and slice. Enjoy warm!
