Set aside 4/5 cup (200 ml) of the milk and dissolve the starch in it. Pour the sugar into the remaining milk and stir until it dissolves.
Heat it in a pot on the stove to boiling point. Pour in the dissolved starch to it and stir until thickened.
Remove from the stove and while still warm, distribute into bowls.
Sprinkle with cinnamon and leave it to cool.