Place the summer fruit into a medium sized pan, add a very small splash of water to stop the fruit sticking, and place over a low heat. When the fruit has defrosted turn up the heat and simmer gently, lid off, until the berries have broken down (about 10 minutes).
Add the sugar and the lemon juice and stir.
Leave to cool for a few minutes then sieve the fruit to remove the pips. Discard the pips, taste the fruit sauce and add more sugar if you like it a little sweeter. Leave to cool completely.
Using a hand held whisk, whisk the condensed milk, double cream and cream cheese together until the whisk begins to leave trails in the mixture, and when you lift the whisk a ribbon of cream falls back into the bowl.
Place ½ the cream mixture to a different bowl and gently fold in the cooled fruit sauce. It does not matter if you don’t incorporate it fully but make sure it’s roughly folded together.
Place the digestive biscuits into a bowl and, using a wooden spoon, crush the biscuits until you are left with lots of small pieces. Fold the little pieces of digestive biscuit into the remaining ½ of the ice cream mixture, discarding the tiny crumbs.
Pour half the biscuit mixture into the dish you will freeze the ice cream in then pour half the fruit mixture on top it. Swirl together using the handle of a wooden spoon. This is a good opportunity to practice getting a good swirl pattern.
Pour the remaining biscuit mixture onto the already swirled ice cream, top with the remaining fruit mixture, swirl.