Place thawed puff pastry sheets on a clean surface and roll each into a 10×12-inch rectangle.
Spread 1 ½ tablespoons of Dijon mustard over each sheet, leaving a ½-inch border.
Layer 6 slices of ham on each sheet, slightly overlapping.
Sprinkle 1 cup of grated cheese evenly over the ham on each sheet.
Roll each sheet tightly from the long edge into a log. Trim the ends for evenness.
Wrap each log in plastic wrap and refrigerate for at least 20 minutes.
Preheat oven to 375°F (190°C). Line two baking sheets with parchment paper.
Slice each chilled log into ½-inch thick pinwheels (about 24 slices per log).
Arrange pinwheels 1 inch apart on baking sheets.
Bake for 18 minutes, until golden brown and cheese is bubbly.
Garnish with fresh herbs if desired. Serve warm or at room temperature.