Preheat the oven to 400°F (200°C). Line a baking sheet with aluminum foil for easy cleanup.
Scrub the potatoes with a scrub brush under running water. Pierce each potato with a fork 2 to 3 times on each side. Place the potatoes on the prepared baking sheet.
Bake the sweet potatoes for 1 hour or until very tender.
Remove from the oven and let cool slightly. Carefully remove the skin of the potatoes (it should easily pull away) and discard.
Place the cooked sweet potatoes in a blender and add ½ cup water. Blend until very smooth, scraping down the sides as needed.
Transfer to a small bowl and let cool, and then serve or store until ready to use. Store in an airtight container in the refrigerator for 3 to 5 days or in the freezer for 4 to 6 months.
