It's a well known halacha that if one intends to eat less than a k'zais of bread then one doesn't make a bracha on al netilas yadayim.
This comes up sometimes on Pesach when there's not enough Matzah to give everyone a whole Matzah (which I presume is a k'beitza since I think a k'zais is about a half of a matzah and a k'beitza is twice that). Does other food combine to the k'beitza or does it have to be a full k'beitza of bread / matzah?
