For the puff pastry, in a freestanding mixer, beat the flour and water together until elastic. Remove half of the dough and roll it into a small rectangle 2.5cm/1in thick. Repeat with the second half, then cover both rectangles with cling film and place in the freezer.
Divide the butter into two and roll out between two sheets of greaseproof paper - a wooden rolling pin will help to flatten the cold butter. Return both slabs of butter to the fridge.
Remove one of the rectangles of dough from the freezer and roll out to double the size of the butter. Keep the second dough in the freezer while you are doing this. Put half of the butter on the top of half of the dough and fold up, sealing the butter into the dough. Roll out to form a long rectangle. Fold the top and bottom in like a book to meet in the middle. Turn 90 degrees and then repeat the rolling and folding. Turn again and repeat the action. Wrap in cling film and return to the freezer.
Repeat this process with the second dough rectangle, sieving the cocoa onto the first lamination.
Perform the lamination process a further two times for each dough, allowing to rest in the freezer for at least 20 minutes each time. While waiting for the doughs to rest make the individual fillings.
For the pesto, blend together all the pesto ingredients in a food processor, adding more oil if required. Put into a jar and keep in the fridge until required.
For the praline paste, line a baking tray with silicon. Dry fry the hazelnuts for a few minutes until beginning to colour. Heat the caster sugar in a pan over a medium heat with 2 tablespoons of water until the colour of caramel. Do not stir after the sugar has dissolved.
Add the nuts to the sugar and pour onto the baking tray. Once solid, break into pieces and blend in a food processor until smooth (about 5 minutes). Store in a jar in the fridge until required.
For the crème légère, heat the milk and vanilla bean paste in a pan until boiling. Whisk the egg yolk, caster sugar and cornflour in a bowl until smooth, before pouring the hot milk on top.
Pour the mixture back into the pan, add the butter and whisk on a medium heat until thickened. Pour into a container, press cling film onto the surface of the cream and allow to cool. Once fully chilled, whisk the double cream in a mixing bowl until soft peaks form when the whisk is removed from the bowl. Stir the cream into the crème légère and whisk until smooth. Store in a container in the fridge until required.
For the ganache, bring the cream to the boil in a pan. Place the chopped chocolate and espresso in a bowl. Pour the cream over the chocolate and espresso and mix until smooth and fully melted. Allow to cool slightly before transferring into a piping bag.
To complete the pastry for the vol-au-vents, preheat the oven to 200C/180C Fan/Gas 6.
Roll the doughs out to 5mm/¼in thick. Using a 5cm/2in round cutter, cut out 24 discs from each dough. Then cut out a 2.5cm/1in circle from the centre. Gather the centres and the scraps of pastry into a ball then re-roll again to 5mm//¼in thick and cut another 24 x 5cm/2in rounds from each dough.
Brush the full discs with a little egg and place a ring on top of each. Using a sharp fork, prick the bottom evenly and all over. Brush with a little more egg. Arrange the vol-au-vents on a large baking tray lined with silicon. Cover with another large sheet of silicon (this helps them to rise evenly). Bake for 15 minutes, checking regularly and only removing the top sheet when fully risen (the chocolate ones might need a little longer). Leave to cool completely. Leave the oven on.
Pipe rounds of ganache into the bottom of the chocolate vol-au-vents and allow to set.
For the savoury filling, add the asparagus, peas, mangetout and broad beans to a bowl, cover with boiling water and leave for 4 minutes to cook gently. Drain all the vegetables, then reserve the very tips of the asparagus for decoration and cut the stalks in half. Add the oil and pesto to the bowl of vegetables and mix well.
Lay the Parma ham flat on a baking tray and bake for 5 minutes, or until fully crisp. Remove from the oven and cut into thin strips.
For the cheese, beat the cream cheese in a bowl with a little salt and pepper and the lemon juice until smooth.
To decorate the savoury vol-au-vents, transfer the cream cheese into a piping bag and pipe a round into the bottom of the plain vol-au-vents. Top with a couple of teaspoons of pesto before adding the vegetables on top until almost full. Pipe a little cream cheese on top and add a Parma ham strip and asparagus tips. Decorate with radishes, micro herbs and a little basil oil. Store in the fridge until required.
To decorate the sweet vol-au-vents, dry fry the hazelnuts and chop. Spoon the praline paste on top of the set ganache. Transfer the crème légère into a piping bag and pipe a blob on top. Sprinkle with the chopped nuts.
Create chocolate curls by using a big flat sharp knife and the bottom of the chocolate bar. Drag the knife over the bar towards you and scoop the curls with the knife - as your hands will melt them.
Sprinkle the chocolate curls on top of the vol-au-vents. The vol-au-vents are best served immediately.