*It can be subbed for Nutella. Toast nuts using skillet. Cook sugar in a hot frying pan until caramel stage. Toss in warn nuts, turn heat off and transfer onto a silicone baking mat to cool. Save one-third for the caramelized nuts; crush them for garnishing.
Heat up milk and throw in hazelnuts; bring to boil and blend. Pass through a sieve and press down to extract as much hazelnut milk. Save solids for later use. Bring back hazelnut milk to the saucepan, add half of the heavy cream and bring to boil. Pour hot liquid into the chocolate and blend. Add gelatin and blend. Add praline and the remaining cold heavy cream. Blend well and refrigerate overnight. Whip the chilled hazelnut ganache to medium-firm peaks and keep refrigerated.
Melt milk chocolate and cocoa butter to 113ºF/45ºC over a bain marie (water bath) on low heat (water should not touch the bottom of the bowl). Wipe off bottom of the bowl and chill it for 5 to 10 min or until the sides of the bowl begins to set, give a good stir and check the temperature; it should be around 80ºF/26ºC. Quickly rewarm chocolate to 85ºF/29ºC and add hazelnut crumbs or grain. Using the tip of a bamboo skewer, dip frozen hazelnut mousse in tempered chocolate. Let set and refrigerate.
Make a 1/4''/6mm thick layer of praliné (hazelnut spread) into each glass. Pipe out some of hazelnut ganache monte (half way through) using the #825 star pastry tip and chill. Use leftover mousse and pipe out into swirls making sure that their diameter do not exceed the size of the cups and freeze until hardened and glaze. Garnish each glass with some crushed caramelized hazelnuts and top with the frozen glazed hazelnut swirl – keep refrigerated until dessert is thawed. Decorate with gold leaf if desired and serve – Enjoy!