Pour the crushed vanilla wafers, chopped nuts, powdered sugar, and cocoa powder into a large mixing bowl. Stir until the dry ingredients are evenly combined.

Add the dark rum and vanilla extract. Mix with a spoon until the liquid is absorbed and the mixture holds together. If it’s too dry, add rum a teaspoon at a time. If too wet, stir in a little more powdered sugar.

Shape the mixture into 1-inch balls using your hands. Press firmly so the balls hold without crumbling.

Pour extra powdered sugar into a shallow bowl. Roll each ball to coat evenly. Shake off excess sugar.

Arrange the coated rum balls on a parchment-lined baking sheet. Refrigerate for at least 2 hours, or until firm.

Serve chilled or at room temperature. Let them sit out 10–15 minutes before serving if you prefer them slightly softer.