Beat egg yolks with powdered sugar and water until creamy, fold in elderberry juice and juice of one lemon. Allow gelatine to melt according to instructions, fold in and set aside to cool until semi-stiff.
Whip whipped cream until stiff and fold in. Set mousse aside to cool.
For the vanilla cream, beat milk with powdered sugar, egg yolks and vanilla pulp while stirring. Soak gelatine according to instructions, squeeze out, fold in and set aside to cool until semi-stiff.
Separately, whip egg whites and whipped cream until stiff and fold in. Divide cream evenly among serving plates and set.
Cut elderberry mousse with a tablespoon and arrange on top of vanilla cream. Garnish with elderberry juice and lemon balm.