About 15 minutes prior, soak the raisins in the dark rum. I gently heat mine in the microwave for 30 seconds to speed things along.

Using an electric mixer, beat the cream, condensed milk, and imitation rum extract in a large bowl on medium-high until stiff peaks form, 3 to 4 minutes.

Drain the excess rum off the raisins and discard. Gently fold in the raisins, reserving some for the topping. Mix until incorporated.

Spoon the cream mixture into a 4 1/2- by 8 1/2-inch loaf pan or 1 1/2-quart freezer-safe container.

Sprinkle the reserved raisins on top. Freeze until set, at least 4 hours.

Once set, cover with plastic wrap and freeze for up to 2 weeks.