For one 8″ cake serving 8 persons.

1 coffee-flavored genoise

1/3 cup of sugar
3 large eggs (1/2 cup)
1-1/2 Tbsp of butter
1/2 generous cup of flour
1 tsp of vanilla sugar
1/2 tsp of coffee extract 
2 generous cups of Chantilly cream (300g)
2/3 cup hazelnuts, whole (100g)
1 cup of syrup, coffee‑flavored   
1 cup generous cup of coffee‑flavored pastry cream

Genoise

• Preheat the oven to 350°F
• Place eggs and sugar in a bowl and over a pot of boiling water.
• Beat for 1 minute.
• Beat in the mixer at high speed for 2 minutes then for 5 minutes at low speed.
• Clarify the butter.
• Mix flour and vanilla sugar and fold it in the egg mixture.
• Add coffee extract.
• Fold in the warm butter.
• Stop mixing as soon as everything is blended.
• Bake right away for 30 minutes in a buttered and floured pan
• Let cool for 10 minutes and turn out into a rack.

Syrup – one cup 

• Place 2/3 cup of water and 1/2 cup of sugar in a saucepan.
• Bring to a boil.
• Cool and add flavorings (3 Tbsp of alcohol or 3 Tbsp of water with 3/4 tsp of coffee extract)

Chantilly – two cups

1 cup heavy cream whipped with 3/4 tsp of vanilla sugar.

Pastry cream

• Place 2 cups of milk with half a vanilla bean split in a saucepan and bring to a boil.
• Beat 2/3 cup of sugar and 6 egg yolks together until it forms a ribbon.
• Gently stir in 4 Tbsp of flour.
• Strain the vanilla bean from hot milk and, slowly at first, add to the egg mixture.
• Pour the whole thing back into the saucepan and bring to a boil stirring constantly.
• Cook for 1 minute.
• Cool in a bowl with a lump of butter brushed on the surface to keep a skin from forming.

Assembling the cake

• Prepare the génoise a day ahead, adding the coffee extract just before adding the flour.
• Whip the Chantilly cream and reserve 1 cup for decorating the cake.
• Refrigerate.
• In the oven, roast the hazelnut and when browned, set aside 20 for decorating.
• Chop or pound the rest.
• Cut the genoise in 3 equal parts.
• Place one layer on a cardboard disk and brush it with the syrup.
• Add 1/2 cup of Chantilly cream to the coffee pastry cream, then add the chopped nuts.
• Cover the first layer completely with half of this cream using a spatula.
• Place a second layer on top, brush with syrup and cover with the remaining cream.
• Place the third layer of cake on top and cover the whole cake with the refrigerated Chantilly.
• Refrigerate for 1 hour.