Put all ingredients in bowl of thermomix and cook for 7 minutes on Speed 4 at 80 degrees. Chill overnight (or for at least 4 hours) in fridge or over ice bath until well chilled, then freeze in icecream maker according to manufacturers instructions. Alternatively, freeze for 4 hours or until firm but not fully frozen, then cut up into pieces and place back in thermomix bowl and mix for 20 seconds on speed 9 and then for 15 seconds on speed 4, using spatula to fell. Put back in freezer to finish freezing