Add the 1/3 of a cup of rum to the raisins, and cover and allow to soak covered at room temperature for 3 – 4 days. Stir a couple of times a day and when you remember. 

To make the cooked ice cream base custard, whisk the egg yolks with the sugar until pale and fluffy. About 3-4 minutes

Add the milk and egg / sugar mixture to a medium pot and heat over low stirring almost continuously until the custard thickens and coats the back of a spoon. About 15 minutes. Strain the mixture through a fine sieve and add the cream, vanilla and rum. Place a piece of cling film over the surface to prevent a skin from forming and chill in the fridge for a few hours or overnight. This also allows the flavours to infuse.

Process the ice cream through your food processor and when its ready add the soaked raisin until evenly distributed. Decant into a freezer safe dish (a metal loaf tin or bowl works well) and freeze until it firms up.