Heat oven to 200 C. Line a baking sheet with baking paper.

Cream together the cream cheese and mustard.

On a lightly floured surface roll puff pastry sheet into 15x12 inch retangle.

Tranfer sheet to the prepared baking sheet; spread the cream cheese mixture longwise on half of the retangle; leaving 1/2 inch border around outside edges.

Add individual layers of ham, onion and cheese over cream cheese layer, leaving a 1/2 inch border around outside edges.

Whisk together the egg and water, brush some of the egg mixture on the uncovered edges of the pastry

Fold uncovered portion of the pastry retangle up and over filling. Use fork to seal edges together. Brush to with egg mixture.

Cut decorated slits in top of pastry for steam to escape.

Bake about 25 minutes or until pastry is golden on the top and bottom.

Enjoy