Remove the seeds and peel the pumpkin, then cut it into small pieces.
Slice the onion thinly.
Melt the butter in a pot and sauté the onions.
Add the pumpkin and stir-fry for 2-3 more minutes.
Pour in the water and simmer until the ingredients are soft.
Turn off the heat and blend everything smoothly with a hand blender or mixer.
Add milk and heavy cream, season with salt and pepper, then heat once more.
Serve in a bowl to complete.