Wash, halve and stone the plums. Simmer juice and plums for 5 minutes, taking 2 halves aside for decoration before they fall apart. Let them cool down and stir in the plum puree. Whip the cream until stiff, add vanilla sugar. Pour into a piping bag with star-shaped spout.
Sprinkle 4 waffles with half of the cream. Add half of the plum compote, 1 wafer each, the rest of the cream and plum compote. Cut the plum halves aside into slices. Decorate the tartlets with them. Serve with mint