Place hazelnuts on a tray in the oven preheated to 190 C / 170 C Fan / Gas 5. Toast gently for 3 to 5 minutes. Remove from the oven. If they have the skin on remove as much as possible while they are warm (it's much easier than when they are cold). Rolling them between your fingers or between a tea towel and the tray is a good way of doing this. Then place the skinned nuts into a blender and pulse until thoroughly chopped. Stop blending before the nuts loose all their texture- you don't want a flour or powder consistency. Set aside the nuts and leave the oven on, ready for the cake.
Prepare the almonds. I prefer to prepare the hazelnuts first so I don't have to wash the blender between nuts, but you may want to do this first while the hazelnuts toast. Place all the almonds into the blender and blend until they form a buttery paste. This may take awhile, from 10 to 15 minutes. I have to stop my blender regularly to scrape the sides down. The resulting mixture should look rather like peanut butter.
Melt the chocolate. I normally do this in the microwave. I put it in small bowl and microwave for 20 seconds at a time on medium, stirring between, until completely melted. Allow to cool (but not set).
Separate the eggs, whites into one large bowl, yolks into another.
Add the honey to the yolks and whisk until pale and foamy. Mix in the chocolate and finally the chopped hazelnuts.
Add the salt to the whites and whisk to stiff peaks.
Fold 1/3 egg whites into the chocolate mixture. The mix will be quite stiff but should loosen up as you stir in the whites. When thoroughly mixed, gently fold in another 1/3 of the egg whites, and finally the last 1/3. You don't want any streaks in the mixture, but try to retain as much air as possible. The thick chocolate mixture will stick to the bottom of the bowl so make sure you scrape it all up and incorporate it. Pour mixture into prepared tin.
Bake for about 30 minutes in the preheated oven. The cake should still be fairly moist when removed from the oven. The skewer test does not work with this cake. I remove when the cake looks moist but no longer 'wobbles' from raw mix when gently shaken.
Decorate with a ganache made from dark chocolate and olive oil, or for cupcakes I normally use buttercream made with dairy free spread.