Carefully defrost the berry mixture on kitchen paper. Grate the zest from the orange and then squeeze the orange. Put the juice together with the zest and the powdered sugar in a suitable bowl. Add the port wine, egg yolks and powdered sugar and beat in a bain-marie with a mixer until the zabaglione has approximately doubled in volume.
Then continue beating in a baking bowl with ice and cool a little.
Divide the berries evenly on dessert plates and spread the port wine zabaione evenly over them. Garnish with mint leaves as desired.