Roughly chop raisins and warm 1/2 cup of rum in a saucepan, add raisins, and stir for 3-5 minutes. Cool completely.

In a bowl, whisk together sweetened condensed milk, 1/4 cup rum, and vanilla powder until smooth.

Stir the cooled raisins into the milk mixture until evenly distributed.

Whip the heavy cream in a separate bowl until stiff peaks form, taking care not to overwhip.

Gently fold the whipped cream into the raisin mixture in two or three additions until well combined.

Transfer to a freezer-safe container, cover tightly, and freeze for at least 6 hours or overnight.

Before serving, let the ice cream sit at room temperature for 5-10 minutes to soften slightly.