So in the Spring a few years ago a woman opened her shade and saw this growing out of the wood in the windowsill. She couldn’t believe her eyes, it even scared her a bit. So she put on a mask and some gloves and proceeded to break off the mushroom and dispose of it properly and clean everything else up with bleach!  There was mushroom dust all over the windowsill as you can see. So what is it?

What is it AND most importantly was it edible?