Preheat your oven according to the puff pastry package instructions.
Roll out the puff pastry sheet on a lightly floured surface.
Cut the pastry into four triangles.
Place a slice of ham and a slice of cheese on each triangle.
Roll up each triangle, starting from the wide end and ending at the tip.
Place the rolled croissants on a baking sheet lined with parchment paper, seam side down.
Brush the croissants with the beaten egg to give them a nice golden color when baked. You can also sprinkle sesame seeds on top if you like.
Bake in the preheated oven according to the puff pastry package instructions, usually around 15-20 minutes, or until the croissants are puffed up and golden brown.
Remove from the oven and let them cool slightly before serving.
Enjoy your homemade ham and cheese croissants!