Hazelnut sponge
Whisk the egg whites together with the sugar until stiff peaks form when you lift the whisk from the mixture.
Weigh out the ground hazelnuts and flour in a bowl.
Preheat the oven to 350°F.
Gently fold the ground hazelnuts and flour into the stiff egg white mixture.
Transfer the mixture to a piping bag.
Place two cake rings (6") on a baking sheet lined with parchment paper and pipe the batter into the rings in circles, ~1" thick.
Bake for 15 minutes or until well risen and the tops of the cakes spring back lightly when pressed with a finger.
Leave the sponges to cool completely.
Shortcrust pastry for base
Mix together all the ingredients in a stand mixer with paddle attachment to form a smooth dough.
Chill in the fridge for about 2 hours.
Roll out the chilled dough between two sheets of baking paper. If the dough sticks to the paper, lightly dust the surface with flour.
Use a 7" cake ring to cut out a circle from the dough.
Cut out a 1/2" wide strip from the remaining dough and wrap it around the edge of the circle to form a border.
Freeze the dough.
Preheat the oven to 400°F.
Bake the frozen dough directly in the oven for 10 minutes at 400°F, then reduce to 325°F and bake for a further 5 minutes until golden brown. Leave to cool completely.
Crunchy cocoa wafers
Mix all the ingredients into a smooth batter using the stand mixer and let it rest, covered, in the fridge for about an hour.
Spread the chilled batter very thinly onto a baking sheet lined with baking paper using a pastry palette. Bake at 400°F for 6 minutes.
Leave to cool completely before spraying both sides with chocolate spray.
Crunchy hazelnut decorations
Mix together the sugar and pectin.
Add all the other ingredients and bring to a boil in a saucepan.
Remove from heat and cool completely.
Roll the cooled mixture into small balls about 1 1/2" in diameter each.
Place them on a baking sheet lined with baking paper, spaced well apart.
Bake at 375°F for about 5 minutes or until golden brown.
Leave to cool completely.
Store in an airtight container to prevent moisture absorption.
Chocolate cream for decoration
Soak the gelatin in plenty of cold water and let it swell.
Slowly heat the milk, cream, egg yolk and sugar in the saucepan at 175°F by gradually adding the egg yolk and sugar while whisking to ensure the mixture doesn't burn.
Stir well to combine, and then pour the mixture over the hazelnut paste and chocolate.
Let the chocolate melt and mix until smooth.
Refrigerate until well chilled.
Whip until you get a stiff cream for piping.
Hazelnut cream
Soak the gelatin in plenty of cold water and let it swell.
Slowly boil the milk while whisking to prevent burning. Once boiled, stir in gelatin until dissolved.
Pour the hot milk mixture over the hazelnut paste and chocolate.
Let the chocolate melt and whisk until smooth.
Whip the cream and fold it into the mixture. Use the hazelnut cream immediately.
Assembling the cake
Pour some of the hazelnut cream into the shortcrust pastry base. Place a crunchy cocoa wafer on top, add more hazelnut cream, and then place a sponge on top to complete the bottom half of the cake.
Place the bottom layer of the cake in the fridge until well chilled.
Pour hazelnut cream into a silicone mold and place a crunchy cocoa wafer on top. Add more hazelnut cream, sprinkle with crushed hazelnuts and add another wafer.
Pour more hazelnut cream into the mold, leaving a gap of ~1/2" from the top. Then, top the sponge and freeze.
Place the frozen top layer on top of the chilled bottom layer. Spray with chocolate spray and decorate as desired.
