Patrick says hi in Italian and cooks them pudding (7)
I believe the answer is:
tapioca
'pudding' is the definition.
(tapioca pudding is a kind of pudding)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for tapioca that I've seen before include "Sago pudding" , "Foodstuff used as a thickener" , "Pudding maker" , "course" , "Starchy foodstuff" .)