Soak gelatin sheets in cold water about 30 minutes before you start.

Place egg yolks and sugar in a bowl and whisk until white and frothy using an electric mixer.

Wash the lemons and finely grate the zest. Then squeeze them.

Remove the gelatin sheets from the water and squeeze out most of the water.

In a small pot, combine lemon juice and softened gelatin.

Melt it over low heat until the gelatin is dissolved. Let it cool until it is almost cold.

Whip the cream to soft peaks.

Beat the egg whites stiff with an electric mixer. Beat until you can turn the bowl upside down without the whites falling out.

Fold whipped cream into the egg mixture with a spatula.

Then stir in the lemon/gelatin mixture - ensure everything is well combined.

Gently fold in the stiffly beaten egg whites at the end - be careful not to deflate the egg whites.

Pour the lemon mousse into a glass bowl and place it in the refrigerator for at least 3-4 hours.

Before serving, decorate the mousse with whipped cream and lemon balm leaves.