It's Parasol season throughout northern Europe; at least I know it is both here and in Norfolk.
I prefer mine in their young state, before they're properly open (above); when the Italians refer to them as Mazza di Tamburo (drumsticks).
Don't bother with the stems, split the caps into 2 or 3 pieces, and fry in Olive oil until lightly browned. Salt very sparingly, and don't add garlic.... they require no extra flavouring.
Don't waste the opportunity; they are one of the best mushrooms available. If you see some, don't kick at them or whack them with your walking stick, pick them and eat them. They're free, and seriously delicious; what more could you ask!