Remove the seeds and peel from the pumpkin, then cut it into small pieces.
Dice the potatoes.
Melt butter in a pot, then add the pumpkin and potatoes and sauté.
Pour enough water to cover the ingredients and bring to a boil.
When the ingredients are soft, turn off the heat and blend smoothly with a hand blender.
Add milk and salt, mix well, and simmer once more.