1. Crush the biscuits in a food processor and mix with the butter. Line a 22 x 22cm square pan (1.2L capacity) with baking paper (this helps with the turning out afterwards) and press half of the crumb mixture on the bottom to form a crust.
2. Allow the ice cream to soften slightly then scoop out long strips with a spoon. Arrange the ice cream on the crust then use the back of a spoon (or the palm of your hand) to press it down. Continue until the pan is full. Now spread the rest of the crust on top of the ice cream in an even layer and also firm down gently. Cover and place in the freezer until hard.
3. Mix the fresh and frozen berries in a mixing bowl and sprinkle with the sugar and lemon juice. Leave for about 30 minutes so that the berries can thaw and the sugar creates the most delicious syrup.