Prepare the hazelnut sponge: Preheat the oven to 170°C. Whip the eggs and sugar until pale and fluffy. Sift together the hazelnut flour, all-purpose flour, cocoa powder, corn starch, salt and baking powder; fold into the egg mixture. Stir in the melted butter. Spread the batter onto a baking sheet lined with parchment and bake until set, about 15 minutes. Let cool, cut out discs and freeze.

Make the mango marmalade: Combine the mango and passion fruit purées in a saucepan. Mix the sugar with the pectin and sprinkle over the purées while stirring. Bring to a boil and cook for 2 minutes. Remove from heat and stir in the bloomed gelatin. Pour into small molds and freeze until firm.

Make the dark chocolate mousse: Bloom the gelatin. Melt the dark chocolates together. Heat the milk with the vanilla until simmering; dissolve the gelatin in the hot milk, then pour over the melted chocolate and blend until smooth. Cool the ganache to about 30°C, then fold in the semi-whipped cream.

Assemble and freeze: Pipe the mousse halfway into silicone molds. Insert a frozen disc of mango marmalade and top with a disc of hazelnut sponge. Fill the molds with more mousse, smooth the tops and freeze overnight.

Prepare the chocolate glaze: Melt the dark chocolate and grapeseed oil together and cool to about 30°C.

Glaze and finish: Unmold the frozen entremets and dip them into the glaze, allowing excess to drip off. Sprinkle with chopped hazelnuts and refrigerate to thaw for several hours before serving.