Peel the pumpkin and clean it of its seeds. Cut it into same-sized pieces. Put it in a small pot with the water and 2 tbsp sugar.
Let it simmer on low heat until it softens (about 20 min). In the meantime, boil the milk.
Dissolve the starch in 2/5 cup (100 ml) of the milk (needs to be cooled, so it doesn't turn lumpy). Put the pumpkin pieces in a deep container and pour in the remaining milk over them.
Mash them together, return to the pot and put on a low stove. Add the remaining sugar to the pumpkin mixture and pour in the starch in a thin trickle.
Add the vanilla and stir nonstop until the cream thickens. Distribute it into bowls and leave them to cool.
Optionally, sprinkle with ground walnuts or cinnamon.