Preheat oven to 200°C. Line 2 baking trays with paper.
Roll out puff pastry into three sheets and set aside.
Make a Bechemel Sauce by placing the egg and yolk, creme fraiche, butter, cornflour and milk into the Thermomix bowl and cooking for 6 min/100°C/speed 4. Cool.
Lay cheese and ham slices across 1 half of each pastry sheet leaving room around the edges to seal. Top with Bechemel and cover with other half of pastry. Seal borders with a fork or small knife. Slash tops to allow steam to escape and brush liberally with egg wash.
Bake for 20-25 minutes until puffed and golden.