dd2 has flatly refused to eat anything containing or touching a potato for the last 18 months (she's 3). However, every time we have potatoes, I've always put one on her plate (just so she can say "I don't like that Mummy" - nice little routine).
ANYway, served up roast chicken, accompanied by a solitary roast new potato as usual.
"I like potatoes Mummy. Mmm, can I have another one?"

Never give up hope.