Preheat the oven to 200C/425F/Gas 7. Line three baking trays with greaseproof paper. You'll also need another baking tray.
For the pastry, sift the flour into a clean bowl. Grate the butter into the flour, add the salt and mix together with a palette knife. Add just enough cold water to form a dough.
Roll the dough out on a floured board into a rectangle, fold it into thirds, turn 90 degrees and roll it out to a rectangle again. Repeat this folding, rolling and truning at least three more times then fold once more, wrap in cling film and chill in the fridge for at least 30 minutes.
Roll the pastry out thinly and cut 36 rectangles, each 10cm x 5cm/4in x 2in. Place 12 onto each baking tray and cover with a sheet of greaseproof paper.
Place the empty baking tray onto one of the trays of pastry ad bake in the oven for 10 minutes. Remove the empty tray and the top layer of paper, dust the pastry with icing sugar and cook for a further 10-12 minutes. Let the pastry cool on a wire rack.
Repeat step 5 with the other two trays of pastry rectangles.
For the coulis, pass the raspberries through a fine sieve, sweeten to taste with icing sugar and spoon into a piping bag fitted with a small nozzle.
For the icing, mix the icing sugar with a few drops of red food colouring and enough water to make a thick paste.
For the filling, spoon the whipped cream into in a piping bag fitted with a plain nozzle.
To assemble the millefeuilles, pipe a little whipped cream onto a pastry rectangle, add a few blueberries and pipe over some raspberry coulis. Cover with another pastry rectangle, repeat the blueberry, cream an raspberry layer then add the top sheet of pastry. Dust with icing sugar and pipe on a strip of the pink icing. Mix together the chopped hazelnuts and orange zest, sprinkle over the icing and garnish with a raspberry and a mint leaf.
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The 12 new bakers don their aprons and head for the iconic tent for cake week.