01 - Preheat oven to 400°F. Line baking sheet with parchment paper.
02 - Unroll puff pastry on lightly floured surface. If using, spread Dijon mustard evenly over surface.
03 - Arrange ham slices evenly over pastry, leaving 1/2 inch border along one long edge.
04 - Sprinkle shredded cheese and chives evenly over ham. Season with black pepper.
05 - Starting from opposite long edge, tightly roll pastry into log toward border. Press edge to seal.
06 - Slice roll into 16 even pieces. Place pinwheels cut side up on prepared baking sheet, spacing apart.
07 - Brush tops with beaten egg for glossy finish.
08 - Bake for 15-18 minutes until golden brown and puffed.
09 - Let cool slightly before serving warm.