Preheat the oven to 180 degrees C/Gas 4 (355 degrees F). Grease a deep 20-centimeter (8-inch) round cake tin.
To make the cake: Begin by grinding the whole almonds with the 50 grams caster sugar in a food processor.
With an electric mixer, beat the whole egg and 5 yolks with the 160 grams caster sugar until the mix is pale and creamy and leaves a trail on the surface. Whisk the egg whites to soft peaks.
Mix the cooled melted chocolate with the egg yolk mixture. Stir in the ground almond mixture and the chopped almonds. Beat in a spoonful of the egg whites to loosen the mixture. Now, a spoonful at a time, gently fold in the remaining egg whites.
Pour the mixture into the prepared cake tin and bake for 40 to 45 minutes.
Once the cake is cooked, leave it in the tin to cool before turning it out onto a serving plate.
To prepare the topping: Place the water, caster sugar, cocoa powder and glucose into a saucepan and bring to the boil. Simmer for 5 minutes and stir.
Soften the gelatin sheets in a little water. Remove the saucepan from the heat. Squeeze any liquid from the gelatin sheets and then add the sheets to the pan. Stir until the gelatin has dissolved. Leave to cool.
Pour the chocolate topping just onto the surface of the cake and decorate with candied lemon peel or extra chopped almonds.