For lilly pilly dressing, combine sugar and 100ml water in a saucepan and bring to the boil, stirring occasionally to dissolve sugar (1-2 minutes). Add lilly pilly berries, remove from heat and set aside until berries are plump (5-10 minutes), then drain. Whisk oil and vinegar to combine, season to taste, then add lilly pilliy berries.
Place witlof leaves in a large bowl, add dressing just before serving, toss to combine and serve with goose ballottine.
Note Lilly pilly berries are small berries that are similar to redcurrants. They are available frozen from select greengrocers and specialty food stores. If unavailable, substitute with frozen cranberries or redcurrants.