Bolete (Boletus) Mushroom

Recently I have purchased dried bolete mushrooms from the store. There appears to be white powder on these mushrooms. When I asked the vendor what the white powder was I did not get a definite answer. Have you ever experienced this before on dried Boletes. If so, are they still edible?

Boletus don't have gills, but form a sponge-like mass underneath. This means the white powder is NOT spore. So what might it be? I have no clue, as Boletus (delicious) are normally yellowish.
Where did the store get them? Start there. As a rule, no problems with ALL forms of Boletus. Hungarian delicacy.