Preheat oven to 325 degrees F (170 degrees C). You will need one loaf tin 7 inches by 2-3/4 inches.
1. Beat egg yolks and sugar until pale and thick. Whisk egg whites and the smaller quantity of sugar until soft peaks form, fold into egg yolk and sugar mixture. Fold in melted butter.
2. Sift flour with unsweetened cocoa powder, add ground hazelnuts and fold into cake batter.
3. Fill prepared loaf tin, make a slight dip in the center.
4. Bake in preheated oven for 35 to 40 minutes. To test for doneness, a knife inserted into the cake's center should come out clean.
5. Remove cake from loaf tin. Trim to even. Slice into three horizontal layers. Make syrup. Bring to boil water and sugar. Remove from heat, add coffee extract and rum. Cool.
6. Prepare ganache. Bring to boil cream and vanilla bean, remove vanilla bean. Pour hot cream onto chopped chocolate, stir until chocolate is melted and smooth. Transfer ganache to a dish and leave to cool.
7. To assemble cake. Brush bottom cake layer with cold syrup. Fill pastry bag fitted with a 3/4 inch (2 cm) flat tip, with ganache. Pipe on a layer of ganache, smooth with a palette knife.
8. Top with second layer and repeat. Place last layer on top, smooth sides with a palette knife.
9. Brush whole cake with syrup, pipe on remaining ganache to completely cover cake. Chill in refrigerator.
10. Glaze. Place cake on a cake rack set over a tray. Pour chocolate glaze over cake. Tap the rack on the tray to settle glaze. Remove any excess glaze, gently press chocolate sprinkles on to cake sides. Chill until firm. Decorate top with chocolate cigarettes, and caramelized hazelnuts.
*If commercial glaze is not available, making it at home can be simple. In a saucepan combine 1 cup cream, 1-3/4 ounces sugar, 1-3/4 ounces glucose (inverted sugar) and 1-3/4 ounces butter. Bring to boil, pour over 1 cup of finely chopped couverture chocolate, stir until smooth. Use while still warm.
Couverture chocolate should always be used in baking as the higher percentage of cocoa butter (usually more than 33 percent) enables chocolate to form a thinner, smooth coating shell and is easier to use.