Wash the grapes and dab dry. Keep 6 grapes for decoration. Pluck the grapes from the stems, cut them in half and remove the seeds. Mix eggs, 50 g sugar, cornstarch and port wine.
Whisk with the whisk of the hand mixer over a boiling water bath until foamy. Pour the grapes into 4 dessert bowls. Pour wine mousse cream over them. Roll 4 grapes in each of the remaining sugar and hang them on the edge of the dessert bowl.
Place the remaining grapes on the edge of the plate. Decorate with mint leaves.