Heat raisins and rum in a small saucepan until just warm.
Remove from heat and let raisins soak for 15 minutes.
Bring milk to a boil in a separate saucepan.
Whisk egg yolks and brown sugar together in a bowl.
Slowly pour boiling milk onto yolks while whisking continuously.
Return mixture to the pan, add cream, rum, and raisins, and cook until thickened without boiling.
Cool the custard completely before churning in an ice cream machine.
Freeze the churned ice cream until firm.
Preheat your oven to 180°C.
Line a 26cm cake tin with greaseproof paper and place on a baking sheet.
Melt golden syrup and 50g of butter together and pour into the tin base.
Arrange seven pineapple rings on top of the syrup mixture.
Finely chop the remaining pineapple and set aside.
Cream the caster sugar and remaining butter until light and fluffy.
Beat in eggs one at a time, then fold in the flour.
Stir the chopped pineapple into the cake batter.
Spoon the batter over the rings and tap the tin to settle.
Bake for 45-60 minutes until golden and a skewer comes out clean.
Cool in the tin for 10 minutes.
Invert onto a plate and remove the paper.
Serve slices with a scoop of the rum and raisin ice cream.