Beat the egg with water in a water bath until frothy. Add the gelatine sheets soaked in cold water and squeezed out and continue beating until the mixture is just lukewarm. Stir in the melted couverture (do not let it get too hot, it should really only melt). Carefully fold in the finely grated pumpkin seeds as well as the pumpkin seed oil and whipped cream and put the mousse in the cold.
Fillet the oranges and drain them. Bring the drained juice with sugar to the boil and thicken very lightly with a little mixed starch, pour over the fillets and allow to cool. Flavor with Grand Marnier.
To serve, distribute the orange fillets on dessert plates. Use a hot spoon to prick the pumpkin seed mousse and add to it. Decorate with roasted pumpkin seeds if necessary.