To make 4 very large croissants, roll the dough out into a 9 x 18 inch (20x45cm) rectangle, and cut the dough into four equal 4½ x 9 inch (11x20cm) pieces. To make six smaller croissants, roll the dough into an 8 x 22 inch (20x56cm) rectangle, and cut the dough into 6 equal 3½ x 8 inch (9x20cm) pieces.
Use a sharp knife to trim the edges on all 4 sides of each rectangle, straightening the edges and sharpening the corners. This also exposes the layers of dough and butter, which will enhance the croissants’ puff.
Line a baking sheet with parchment paper. Divide the ham and cheese into 4 portions for larger croissants (¾ ounce/20g each) or 6 portions for the regular croissants (½ ounce/14g each) Arrange the ham and cheese (they can be in pieces) in a small 3x3-inch (7.5x7.5cm) square.
Place ham and cheese in the middle of the dough rectangles, and fold both sides of the dough over the top so they overlap. Place on the prepared baking sheet so they are seam-side down, spaced at least 2 inches (5cm) apart.
Cover the croissants with a clean, dry kitchen towel, and let them proof on the counter for about 90 minutes at about 70-75°F (21-24°C). The croissants should look puffy and light after proofing.
Arrange a rack in the middle of the oven, and preheat to 425°F/220°C. Gently brush each croissant with the egg wash, avoiding the laminated edges as best you can.
Bake the croissants for 6 minutes, then rotate the pan 180° and bake for another 6 minutes. Then reduce the oven temperature to 350°F, and continue baking for another 15 to 18 minutes (again rotating them hallway through for even baking) until they’re an even golden brown.
Remove from the oven and let cool for at least 15 minutes before enjoying.
Notes
Nutrition information is per croissant, if you make 6 croissants. Prep time includes time to make croissant dough.