For the Praline Chocolate Crunch:

1 1/2 cup sugar
1 1/2 cup blanched hazelnuts, toasted
1 tsp. vegetable oil
4 oz dark chocolate, chopped
4 oz milk chocolate, chopped
1/4 tsp salt
2 cup puffed rice cereal

For the Chocolate Sponge Cake:

1 cup all purpose flour
1 cup unsweetened cocoa powder
8 large eggs
1 cup sugar, divided
2 Tbsp light corn syrup
1/3 cup brandy

For the Hazelnut Ganache:

1/2 cup heavy cream
1/2 cup ground roasted hazelnuts
1/4 tsp salt
3/4 cup unsalted butter, room temperature, cut into tablespoons

For the Praline Mousse:

4 oz dark chocolate, chopped
1 cup hazelnut praline paste (reserved from praline chocolate crunch)
5 Tbsp unsalted butter, room temperature, cubed
1 3/4 cup heavy cream, chilled and divided