01 - Preheat oven to 400°F. Line baking sheet with parchment paper.
02 - Unroll puff pastry on lightly floured surface. Spread Dijon mustard evenly over surface if using.
03 - Arrange ham slices evenly on pastry, leaving ½ inch border along one long edge. Sprinkle shredded cheese and chives over ham. Season with black pepper.
04 - Starting from opposite long edge, tightly roll pastry into log toward border. Press edge firmly to seal.
05 - Slice roll into 16 even pieces. Place pinwheels cut side up on prepared baking sheet, spacing apart.
06 - Brush tops with beaten egg for glossy finish.
07 - Bake for 15-18 minutes until golden brown and puffed.
08 - Let cool slightly before serving warm.