Beat flour and water in a mixer until elastic, divide into two 2.5cm rectangles, and freeze.
Divide butter into two portions, roll flat between greaseproof paper, and chill in the fridge.
Roll first dough rectangle to double the butter size, seal butter inside, and perform book folds.
Repeat lamination with second dough rectangle while sieving cocoa onto the first layer.
Laminate both doughs twice more, resting in the freezer for 20 minutes between folds.
Blend pesto ingredients in a food processor and chill in a jar.
Dry fry hazelnuts then heat sugar and water in a pan to create caramel.
Combine nuts and caramel, cool, then blend into a smooth paste.
Boil milk and vanilla, then whisk into egg yolk, sugar, and cornflour.
Thicken custard with butter on heat, cool, and fold in whipped double cream.
Pour boiling cream over chocolate and espresso, mix until smooth, and transfer to a piping bag.
Preheat the oven to 200°C.
Roll doughs to 5mm thick and cut 24 discs and 24 rings from each type.
Assemble pastry rings on discs with egg wash, prick bases, and bake for 15 minutes.
Pipe ganache into the cooled chocolate pastry cases and allow to set.
Blanch asparagus, peas, mangetout, and beans in boiling water for 4 minutes then mix with pesto.
Bake Parma ham for 5 minutes until crisp and cut into thin strips.
Beat cream cheese with lemon juice, salt, and pepper until smooth.
Assemble savoury vents with cream cheese, pesto, vegetables, ham, and micro herbs.
Top chocolate ganache with praline paste, crème légère, and chopped toasted hazelnuts.
Shave dark chocolate bar with a knife to create chocolate curls.
Garnish sweet vol-au-vents with chocolate curls and edible flowers before serving.