Put the ground hazelnuts in a saucepan and roast a little while stirring, until it begins to smell intensely of hazelnuts. Then remove the saucepan from the stove and add the cream and milk and stir well. Season with cinnamon to taste.
Soak the gelatine in cold water. Separate the eggs, add the yolks to the hazelnut milk and park the egg whites in the refrigerator. Mix the egg yolks well with the hazelnut milk and put back on the stove and heat while stirring until the mixture starts to thicken.
Then remove from heat and stir in the squeezed gelatin. Now puree everything with the magic wand for about 2 minutes, this will give the mousse a really nice, fluffy consistency. Now let the mixture cool down a little.
In the meantime, beat the egg white with a pinch of salt until it is stiff, then continue beating while slowly pouring in the sugar. Carefully fold the egg whites under the hazelnut mixture, pour into dessert glasses and let set in the refrigerator.