Hazelnut Genoise:
Preheat the oven to 350F (180C) and place the rack in the lower third of the oven.
Put the flour, hazelnut powder, and cornstarch in a food processor and pulse for 30 seconds.
Repeat the operation 10 times to obtain a fine and well-mixed powder. Set aside.

Beat the egg yolks and 3/4 cup (150g) of sugar until the mixture is white.
Add the vanilla extract and lemon zest. Set aside.
Add the dry ingredients and mix well, then incorporate the clarified butter.
Beat the egg whites until stiff peaks form, incorporating the remaining 1/4 cup (50g) of sugar.
Incorporate the egg whites by folding,
Pour the batter into a 9″ x 13″ x 2″ (23cm x 33cm x 5cm) rectangular mold with removable sides and smooth the top.
Bake for 30 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool completely on a rack.

Syrup:
Mix all the ingredients in a saucepan and bring to a boil.
Reduce for 5 minutes. Let cool and set aside.

Hazelnut Praline:
In a pan, roast the hazelnuts dry.
Sprinkle the hazelnuts with sugar and caramelize.
Pour the preparation onto a silicone mat and let cool completely.
Break the preparation into pieces and transfer it to a food processor to grind.
Set aside.

Praline Butter Cream:
In a stainless steel bowl, beat the eggs, sugar, and orange liqueur with a whisk.
Heat the mixture over a bain-marie and beat with an electric mixer until the mixture reaches 65C.
As soon as the mixture is at the right temperature, remove the bowl from the heat and beat with an electric mixer until cooled.
Incorporate the soft butter and praline, and continue beating with a whisk.

Apricot Glaze:
Put the jam and water in a saucepan and heat for 2-3 minutes, stirring to prevent sticking. Set aside.

Chocolate Glaze:
Heat the cream and corn syrup until boiling point.
Pour over the chocolate and mix until the chocolate is melted.
Add the orange liqueur, vanilla, and water, and mix.
Let cool so that the ganache thickens and can be worked to glaze the cake.

Assembly:
Cut the cake into 3 equal rectangles.
Brush the first rectangle with syrup.
Glaze with apricot glaze.
Spread the praline butter cream.
Repeat the operation 2 times, ending with the praline butter cream.
Refrigerate.
Glaze the cake with the chocolate ganache using a spatula, then decorate with caramelized hazelnuts.
Refrigerate for 3 hours before serving.