Wash oranges, take off zest, cut them into halves and press juice. Store the orange juice in tightly closed container in a fridge.

Shred the zest, cover with hot water and simmer for 5 minutes, strain then and cool down to 40C, add sugar and dissolved gelatin. Bring to a boil, stirring. Blend with the orange juice and cool until viscous mixture formed.

Beat the mass in a mixer until stiff foam. If it fails to stiffen well, cool it down again and continue beating.

Pour the neaten mass into molds and cool until congeals.

Unmold the mousse before serving, plunging the molds into hot water for several seconds and turning the mousse into ramekins or dessert plates. Cover with fruit syrup if desired.