Neapolitan ice cream sandwiches

Method

1. Pour the milk and cream into a pan with the split vanilla pod. Bring almost to the boil, then remove and leave to infuse for 20 minutes. Whisk the egg yolks in a large bowl with the caster sugar. Pour the vanilla cream and milk mixture over the yolks, whisking to a custard. Pour back into a large clean pan and set over a low heat. Stir constantly until thickened enough to coat the back of the spoon. Pass through a sieve into a large jug, discarding the vanilla pod, then divide among 3 large bowls. Put a layer of cling film on the surface to prevent a skin forming, then leave to cool.
2. Grease and line 2 x 23cm square brownie tins with cling film, making sure it overlaps the sides by 10cm or so. For the lemon ice cream layer, fold the lemon curd and lemon juice through one of the bowls of custard, then churn in an ice cream maker until softly frozen. Divide between the tins, spreading evenly, then pop them in the freezer.
3. For the strawberry ice cream layer, mix the strawberries with the sugar in a bowl and leave for 15 minutes. Blend to a purée in a food processor. Fold through one of the bowls of custard, then churn in an ice cream machine until softly frozen. Remove the tins from the freezer and divide the ice cream between them. Smooth over the top, then put back in the freezer.
4. For the blueberry ice cream layer, put the sugar in a pan with the blueberries and 50ml water. Bring slowly to the boil, then simmer for 10 minutes, stirring occasionally, until the berries soften and release their juice. Blend in a food processor, then push through a sieve (in batches if need be) to remove the skins. Cool, then fold the syrup through the remaining bowl of custard. Churn in an ice cream maker until softly frozen. Pour over the strawberry layer, spreading evenly. Fold over the excess cling film to cover, then freeze for a few hours or until frozen.
5. To serve, remove the ice cream from the tins – use the cling film to help – then peel it off. With a large sharp knife, cut each block into 15 bars. (Dip the knife into hot water, then dry the blade to make slicing easier.) Sandwich the bars between 2 wafers and eat with your hands.