Lightly flour a clean work surface. Flour a rolling pin and roll out each puff pastry sheet to flatten the seams. Lay the sheets 2 by 2.
2. Step
Make a diagonal cut across the 2 bottom sheets of puff pastry from the lower right corner to the midpoint on the left side of the lower left sheet.
3. Step
Make another diagonal cut across the 2 top sheets of puff pastry from the upper right corner to the midpoint on the left side of the upper left sheet.
4. Step
Holding the bottom pieces together, rotate clockwise 180˚ and up, so that the left side of the bottom strip meets the left side of the lower middle strip.
5. Step
Holding the top pieces together, rotate counterclockwise 180˚ and down, so that the left side of the top strip meets the left side of the up middle strip.
6. Step
Seal the seams by brushing a bit of egg wash where the pieces of pastry meet, overlapping the pieces slightly, and pressing together.
7. Step
Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
8. Step
Arrange the cheese slices in a single layer across the lower portion of the triangle. Top with a single layer of ham slices.
9. Step
Roll up the puff pastry from the base of the triangle to the top point.
10. Step
Place the croissant on the prepared baking sheet and cover with aluminum foil.
11. Step
Bake for 45 minutes.
12. Step
Remove the croissant from the oven, take off the foil, and brush the croissant with egg wash.
13. Step
Bake for another 1 hour and 15 minutes, until the croissant is golden brown.
