Separate the eggs. Beat yolks with the sugar until the mixture becomes light in colour. Soak gelatine leaves in cold water for 5 minutes then dissolve them in a cup with 2 tablespoons boiling water. Grate the peel of the lemon and mix into the egg mixture. Squeeze the juice of the lemon into the gelatine mix. Add this to the egg mixture and stir the mixture smooth.
 Whip the cream stiff and mix into the egg mixture. Use a wire whisk to remove all lumps.
 Finally put the egg whites in a completely clean bowl and whip until you have fluffy white foam. Fold it into the mousse mixture and stir gently with a wire whisk so the mixture is completely smooth and lump free.
 Pour the dessert in a dessert bowl and place in the refrigerator for a few hours, until the mousse has set.
 Just before serving, whip eggs and sugar until thick, fluffy.
 Take the mousse from the refrigerator and bring out the white tablecloth and silverware.
1) It is important that eggnog is whipped just before serving. After a while it will lose some of airiness and separate a little. Mousse however you can make the day before serving.
2) Some people like to vault the mousse out of the mould and onto a large serving dish with edges, and then pour the eggnog over the mousse before serving.