Mix the yogurt with the mixed berries and add to the tray to a thickness of about 1cm.
Taking a tablespoon of jam, swirl it around the yogurt to create a wave. We used raspberry jam, however any jam would work - even peanut butter would be nice.
Spread out the nuts (you can chop them if you want). You can always add chocolate if you want something sweeter.
Cover with clingfilm and place in the freezer for 2 hours until set or overnight. Cut and enjoy.