Wash sweet potato and pumpkin thoroughly, peel them, and cut into cubes.
Put sweet potato and pumpkin in a pot, add enough water to cover, and boil.
Drain the cooked sweet potato and pumpkin.
Place the boiled sweet potato, pumpkin, and soy milk in a blender and blend until smooth.
Transfer the blended mixture to a pot and heat over low heat, stirring gently.
Season with salt or honey to taste.