Place the sliced bananas in a sealed plastic bag and put them in the freezer for 1 hour. Place
the brown sugar and 1/4 cups hazelnuts in a blender and grind together until fine. Place the frozen
bananas, ice cubes, milk, and rum in the blender with the sugar and nut mixture. Blend until
smooth. Pour the smoothies into 4 goblets or tall glasses. Garnish with chopped nuts, if desired.