For the millefeuille:
For the raspberry sauce:
Preheat the oven to 200C/390F/Gas 6.
To make the pastry, tip all the ingredients into a large bowl, mix together with your hands until it all comes together. You may need a splash more of water, tip onto a floured surface and roll out into a large rectangle, fold into a book turn then roll into a rectangle and do another book turn.
Repeat once more brushing off any excess flour as you go. Roll out to 3 mm thick, cut into 10 cm circle and pop onto a baking tray. Dust in icing sugar and bake the pastry in the oven for 15 minutes, or until golden-brown and well risen.
Remove from the oven and set aside to cool.
Whisk the double cream in a large bowl until soft peaks.
For the raspberry sauce, place the raspberries into a food processor and blend to a smooth purée. Pass the mixture through a fine sieve into a bowl.
To serve, split both pieces of pastry in half widthways to make 3 pieces of pastry. Place one piece in the centre of a serving plate and pipe over the crème pâtissière cream mix.
Arrange fresh raspberries on top of the cream, then top with another sheet of pastry.
Repeat the layering process by topping the second sheet of pastry with half of the remaining cream and some more raspberries.
For the final layer, top the last piece of pastry with the remaining raspberries and dust with icing sugar. Serve each slice of millefeuille in a pool of the raspberry sauce and a sprig of mint.