What movie is with this plot?

I remember this movie on Disney (I think) where the main character is
a boy with the power to make food out of thin air. He later learns
that he inherited this power from his grandmother and he uses this to
impress people and win contests, which in turn causes his power
degrade.

One thing I also remember is that the more they reveal to people that
they have this power, anything they conjure will turn out bad or an
utter failure.