Clean, wash and drain the cherries. Mix with sugar and fill up with rum. Pour into a large preserving jar (approx. 1 litre capacity) and close it. Leave to stand for a few days. Stir several times. Just before serving, whip cream and vanilla sugar until stiff. Serve rum-cherries with ice cream scoops, tuffs of vanilla cream and, if desired, garnished with biscuits and mint