Charles dished up a pudding to one surprised A-level student when he visited Carshalton Boys Sports College with celebrity chef Jamie Oliver.
The heir to the throne stepped into the kitchen of the school in Carshalton, south London, to learn about the healthy eating options that have replaced burgers and chips.
Rosie Wastell, 17, was left red-faced when she found Charles behind the serving hatch taking her order for rhubarb crumble.
But he forgot about the famous school custard which had to be poured by dinner lady Sandra Rudge, 43, who said: “He should come and work with us, he’s a character – he’s lovely.”
Speaking about Charles’s omission of the custard, she added: “He doesn’t know what he’s missing.”
Rosie said about being served by the heir to the throne: “I think it’s cool, but a bit embarrassing. He said if I want more I could come back.”
Headteacher Simon Barber began the initiative to encourage his pupils to grow and cook their own produce, and today the school keeps chickens for eggs and grows a variety of crops from strawberries and lettuce to herbs.
The meals served to pupils have also changed with frozen dinners replaced by fresh dishes like salmon with coriander and beef bourguignon.