1 oz of Dark rum
1/2 oz of 151 proof rum (or overproof rum)
2 tsp of white creme de menthe (or Mint liqueur)
1/2 oz of Light Cream
1/2 oz of dark creme de cacao (or chocolate liqueur)
In a shaker half-filled with ice cubes, combine all of the ingredients. Shake well. Strain into a cocktail glass.