List of ingredients:

4 egg yolks.
2 grated lemons zest.
1 envelope of gelatin.
2 cups of heavy whipping cream.
2/3 cup of sugar.
½ cup of lemon juice, strained.
4 tablespoons of white rum.
Whipped cream, to garnish.
Berries, to garnish.

Method of preparation:

In a mixing bowl, combine the egg yolks, grated lemon zest, lemon juice and sugar.

Place over gently simmering water, and whisk until thickened.

Remove from the heat, then beat with whip on medium speed until cold and thick.

In a heatproof bowl, combine the gelatin and white rum, allowing to soak for about five minutes.

Place the bowl over a pan of simmering water until melted. Remove from heat and allow to cool slightly.

Whip the cream on medium speed until it just holds its shape.

Whisk the gelatin into the egg yolk mixture.

Fold in the whipped cream.

Pour the mousse into a bowl or individual glasses.

Garnish with whipped cream and berries.

Source: http://www.lemonrecipes.net/lemon-mousse.html

For more similar dessert recipes, see the official mousse recipes website.