Lemon Mille-feuille

1. Preheat the oven to 200 C / 400 F and roll the puff pastry into a thin rectangle, prick it all over with a fork, brush with the beaten egg and place a second baking tray on top to keep it flat.
2. Bake the weighted pastry for 18 to 20 minutes until crisp and deep golden, then cool, dust generously with icing sugar and briefly grill or blowtorch to caramelise; cut into 12 equal rectangles.
3. For the lemon custard, whisk the egg yolks, whole egg, castor sugar and flour together until smooth and pale.
4. Heat the milk with the lemon zest until just steaming, then pour it slowly onto the egg mixture while whisking constantly.
5. Return everything to the pan and cook over medium heat, stirring continuously, until the custard thickens and bubbles for about a minute, then take off the heat and beat in the lemon juice and butter.
6. Press cling film directly onto the surface of the custard and chill until cold and set, then spoon it into a piping bag.
7. Pipe a layer of lemon custard onto a pastry rectangle, top with a second rectangle, pipe again and finish with a third piece, then dust the tops with icing sugar and serve.

You'll use: Oven · Grill / broiler · Pan · Whisk · Baking tray