Take 2 sheets of puff pastry out of the freezer to defrost for about 30 mins.
Unfold the pastry and roll it out a bit to smooth out the creases. Don't press too hard you don't want to thin out the pastry. With a sharp knife, cut each sheet into 9 equal pieces by cutting 3 rows down and 3 rows across.
Place the squares on a baking sheet lined with parchment paper. You may need two baking sheets to fit them all.
Place the squares back into the freezer for 15 mins and in the meantime preheat your oven to 400℉.
Prepare the egg wash by mixing 1 egg with 2 tbsp water and whisk vigorously.
After 15 mins, take the pastry out of the freezer, brush with eggwash and then straight into the hot oven. This will ensure you get a nice puff. Bake for 20 - 30 mins, depending on the oven.
Add the set pastry cream to a piping bag with no tip. Once golden brown, take out of the oven and place on a wire rack to cool.
Once cooled, using a serated knife, gently cut the pastry in half horizontally.
Then pipe the pastry cream onto the bottom part of each pastry (be generous) and place the top on.
Sprinkle with lots of confectioner's sugar and serve.