In a small bowl combine rum and raisins. Allow raisins to rest a couple hours to macerate.

Place a small pot inside a larger pot filled partially with water to make a double boiler. In the top pot, add sweetened condensed milk and chocolate chips

Heat the pot over low heat to gently melt the chocolate, stirring constantly to prevent burning.

Reserve ¼ cup of raisins for garnish. When the chocolate is completely melted, thick and smooth, stir in the remaining raisins and rum. Stir until fully incorporated and remove from heat.

Lightly grease and line 8x8-inch baking dish with parchment paper. Pour chocolate mixture into the prepared baking dish, gently tapping the dish to smooth out the fudge surface and to remove air bubbles.

Sprinkle top evenly with reserved raisins.

Refrigerate fudge for at least 4 hours to set. Lift the paper containing the fudge out of the pan and cut fudge into 1-inch pieces or desired other size. Dip your knife into a glass filled with hot water between slices if it is starting to stick to the fudge.

Dust with powdered sugar and cocoa powder (optional) and serve.