Use Silikomart sphere mold Ø58, and half mini-sphere silicone mold (Available on the Shop Page).
Heat up cream, milk, sugar, corn syrup, salt and vanilla; keep hot. Meanwhile, make a caramel with sugar and glucose. Carefully, when the caramel is ready – turn the heat off and pour the hot cream mixture in thin stream (wear gloves to prevent burning). Turn heat back on and cook the caramel mixture to 221ºF/105ºC. Pass through a sieve and cool to 158ºF/70ºC, add butter and blend well. Set aside.
Mix soft caramel with milk and chill.
In a food processor, blend until it turns to paste.
Toast nuts in 350ºF/180ºC oven for about 12 min; cool. In a hot saucepan, cook sugar to caramel stage. Toss in nuts and transfer caramelized nuts on a silicone mat. Let cool and break into pieces. In a running food processor, add a pinch of salt and turn caramelized nuts into paste.
Soak gelatin sheet in cold water to soften, and drain. Heat up milk, throw in toasted hazelnuts and blend well. Cover and let infuse 20 min. Drain pressing down solids to extract as much flavor as possible. Save solids for later use if desired. Add one-third of the heavy cream into the hazelnut-milk; heat up (almost to the boiling point) and pour in white chocolate and blend well. Add gelatin and the hazelnut paste; blend well. Add remaining chilled heavy cream and blend. Chill overnight. Whip to soft peaks before using.
Cream butter and hazelnut paste. Separately, beat yolks and sugar and combine both mixture. Meanwhile, make a meringue with the egg whites and sugar. Fold meringue into the yolk-hazelnut mixture. Spread onto a small baking tray lined with a greased parchment. Top evenly with crushed hazelnuts and bake at 350ºF/180ºC for about 18 minutes.
Use a 1.18''/3cm diameter cookie cutter, and cut out hazelnut sponge disks; save leftovers. Pipe out a dollop of hazelnut praliné inside each mini half-sphere silicone mold, add hazelnut sponge disks and more hazelnut praliné – smooth out and freeze to harden. Remove from mold and keep frozen.
Fill each half sphere mold with the whipped hazelnut mousse. Freeze for about 30 minutes. Using a small ice cream scoop, create a cavity the same size as the half mini-sphere silicone mold. Fill cavities with the soft caramel for inserts and freeze for 30 min. Top with a frozen praliné insert. Enclose with the silicone mold lid. Fill up each cavity with the remaining mousse. Freeze for at least 6 hours or overnight. Remove from mold, and shave off bottoms a bit to stabilize the cake. Pipe out a dollop of hazelnut mousse on top of each cake and carve out to mimic the shape of the hazelnut and freeze to set. Wear gloves, and smooth out the surface of each cake. Keep frozen.
Melt cocoa butter to 175ºF/80ºC first and pour in milk chocolate, blend and sieve. Use at 113ºF/45ºC. Insert a bamboo skewer in each frozen hazelnut cake (one at the time), immerse in milk chocolate shell glaze. Lift up and rotate until the chocolate sets. Brush off the sides of the glazed cake using a wire brush. Remove bamboo skewer. Dust gold powder and refrigerate. Repeat until done.
Cut out plastic acetate sheet into 10 each 7.5''x2''20x5cm strips. To temper dark chocolate couverture: Melt dark chocolate over water bath to 122ºF/50ºC. Refrigerate a few minutes until temp reaches 79ºF/26ºC. Carefully, rewarm chocolate to 87.8/32ºC. Spread some dark chocolate on the plastic strip, brush off sides to mimic hazelnut leaf – place the finished hazelnut cake in the center and wrap in contact carefully without any excessive pressure. Refrigerate to set. Thaw 6 hours in the refrigerator prior plating. Enjoy!