Preheat the oven to 200C, 180C fan, gas 6. Line a baking sheet with greaseproof paper.
Open the Croissant dough can, unroll the dough and cut along the perforated lines.
Brush each triangle with beaten egg and lay a slice of ham in the centre of the triangle. Sprinkle a little of the cheese along the bottom half of the triangle. Fold the top point down to the left hand corner point, sealing the sides together by pressing a fork gently down the open sides. Fold the third triangle point over the top encasing to form a triangular parcel. Seal by pressing a fork along the pastry edge, then turn over and place on the baking tray. Repeat with the remaining 5 croissants.
Brush with beaten egg, and sprinkle with cheese. Bake in the oven for 10-12 minutes, until cooked and golden. Remove and serve.