"Pöllö tahtoo vihreää jäätelöä" should be accepted
...just leave it in the fridge for a few years, pöllö
There is word "some" in English, wich is not in Finnish.
The partitive endings on vihreä-ä and jäätelö-ä expresses the meaning of "some".
Curious why the english sentence we need to translate has 'Pöllö' already?
It implies it's a name here, and not an owl.