Carolyn Robb, 53, would make puddings the size of 50 pence for the princes, and recalled the time Harry came down to the kitchen at Kensington Palace “before breakfast and asked for [a treacle tart].”
Ms Robb, who began working for Charles and Diana in 1989, told the young royal that he’d have to ask his mother.
“So off he went, scampering back a few minutes later with a note Diana had written: ‘Mummy says it’s okay,'” Robb told The Sunday Times.
Ms Robb also revealed the likes and dislikes of the Royal Family – William preferred chocolate biscuit cake, while the Queen is partial to roast pheasant.
She added Diana was “very easy to cook for and loved simple things”, such as “cold minted lamb, salads, souffles, stuffed aubergine”.
The princess also “often helped with the washing up”.
In comparison, Prince Charles “could be more demanding” and insisted on eating what “was in season in the garden”.
William and Harry were 15 and 12 when their mother Diana was killed in a car crash in Paris in 1997.