France has issued many stamps on food (not foodstamps!) on her own gastronomy for quite some time including the new series will be issued on April 25th and wil be printed in the form of mini-sheets dedicated to a particular region with stamps, pics and explanations.
As for stamps issued since the first stamp in 1849, a great number of them were issued with edible mushrooms as a theme:
CHANTERELLE VIOLETTE/Violet Chanterelle
ORONGE/Amanita Caesara: The Mushroom of the Cesars!
TROMPETTES DE LA MORT/Black Trumpets
Look forward to the next postings! There are plenty more!