01 -
Heat the oven to 400 F. Line two baking sheets with parchment paper.
02 -
Lightly flour the counter and roll each cold puff pastry sheet just enough to smooth the seams. Cut each sheet into 6 rectangles for 12 total pieces.
03 -
Stir the Dijon mustard and honey together in a small bowl. Brush a thin layer on one half of each pastry rectangle, leaving a 1/2-inch border.
04 -
Top the mustard with ham, Swiss, Gruyere, herbs, and black pepper. Keep the filling centered so the edges can seal cleanly.
05 -
Fold the pastry over the filling. Press the edges firmly with a fork, then cut a small vent in the top of each pocket. Chill the tray for 15 minutes.
06 -
Whisk the egg with 1 tablespoon water. Brush over the pastries and sprinkle with seeds if using. Bake for 18-22 minutes until puffed, deeply golden, and crisp.
07 -
Let the pastries rest for 5 minutes before serving so the cheese settles slightly and the layers stay flaky.