Peel plantain by running the tip of a knife into the peel from top to bottom, 3-4 times. Use your fingers to peel away the skin. If you have trouble, just cut the peel off with a knife.
Cut plantain into smaller pieces and add to blender along with water. Blend on high until the mixture is completely smooth without lumps.
Pour the plantain mixture into a medium saucepan, add vanilla bean, cinnamon and mace, and set aside while you prep the milk.
Rinse the blender out and add pitted dates and milk, blending on high until the dates are completely pureed. Set aside.
Cook the plantain mixture on medium-high heat, stirring constantly to avoid lumps and burning, for about 5 minutes or until plantain mixture is thickened, opaque, shiny and smooth.
Remove the saucepan from heat and pour in the date-milk mixture.
Return the saucepan to medium-high heat, stirring constantly, until the porridge bubbles and has a thick yet pourable consistency. If it's too thick stir in a bit more milk. Remove from heat and stir in grated nutmeg.
Serve hot, topped with fresh coconut milk, banana slices and a sprinkle of grated nutmeg. Enjoy!