Ummul Mu'mineen Hazrat Aishah radiyallahu anha says, Rasoolullah sallallahu alaihe wasallam used to come to me and ask if there was any food available. When I would say, "No," he would say, "I have intended to fast."Once when Rasoolullah sallallahu alaihe wasallam came and enquired, I replied, 'We have received a present.' Rasoolullah sallallahu alaihe wasallam asked, 'What is it?' I replied, 'Malidah (a type of cake made of dates, ghee, cheese or flour).' He said, 'I had made an intention of fasting already.' He then ate some from it.
English reference: Book 25, Hadith 173
Arabic reference: Book 26, Hadith 182