Mix yoghurt, vanillin sugar, sugar and 2 tablespoons of lemon juice. Peel and slice the kiwis. Peel and slice the bananas. Arrange kiwis and bananas in a fan shape on four plates, sprinkle with remaining lemon juice and sprinkle with brown sugar. Serve decorated with lemon balm and lemon slice as desired. Serve the yoghurt in a small bowl, decorated with lemon balm and lemon, as desired