Definition of truffles:
(n) :
Any of various edible fungi, of the genus Tuber, that grow in the soil in southern Europe; the earthnut.
(n) :
(by analogy) Ellipsis of chocolate truffle (“creamy chocolate confection, in the form of a ball, covered with cocoa powder”). [A confection having a center of ganache and an outer coating of powdered cocoa or chocolate.]