Clean and wash the rhubarb and cut it diagonally into pieces about 7 cm long. Boil 250 g sugar, 50 ml water, cassis liqueur and cinnamon stick in a pot. Add the rhubarb and cook for 3-4 minutes.
Remove the rhubarb pieces and let the juice boil down thickly or mix cornstarch with a little cold water and thicken the juice with it. Remove the cinnamon stick, add the rhubarb and keep warm.
Wash the lemon and lime thoroughly and grate the peel finely. Squeeze the juice from both fruits. Separate 1 egg. Place the egg yolks, whole egg, 40 g sugar, cachaûa, white wine, lemon and lime juice in a metal bowl and beat warm on a hot water bath (until a temperature of 85 ° C is reached).
Lift the bowl out of the water bath and stir until slightly cold. Beat egg white and remaining sugar until stiff. Whip cream until stiff as well. Fold 2/3 of the lime and lemon peel, cream and egg white into the foam mixture.
Arrange the rhubarb compote on plates and cover with the sabayon. Sprinkle with remaining lime and lemon peel and a little cinnamon. Serve decorated with mint.