Soak the gelatine in a little water for about 10 minutes.
Peel the parsnips and apples. Remove the core from the apples. Cut the parsnips and apples into small pieces and cook them in a saucepan with a little water. Puree finely, allow to cool, season to taste, possibly sweeten a little.
Beat the egg whites until stiff. Whip the cream. Fold the egg white and cream into the parsnip and apple sauce. Stir in the tonka bean syrup.
Squeeze out the gelatine and heat it in a saucepan until it dissolves. Mix a teaspoonful of the apple and parsnip mixture into the gelatine (temperature compensation) and then stir this mixture into the mousse. Season again to taste and if necessary sweeten or add a little more syrup.
Pour the mousse into a bowl or in portions into small bowls and chill for approx. 2 to 3 hours.
If more than 4 proteins have to be used, that is not a problem. The mousse will then be a little fluffier.