I came across one Viperon the Pembrokeshire Coast Path one time - right between my legs as I stopped to take in the view!
Panic reaction had me stomp its head to pulp (sorry!) but waste not want not as they say....I skinned cleaned and cooked it - and ate it.
Skinning was quite difficult as I remember, gutting it I cannot realy recall (it was about 25 years ago dammit!) and I fried it a little at a time on a Gaz Globetrotter stove.
I may well have overcooked it but it was chewwy, boney and a bit like, yeah thats right, chicken!
The most Vipers I have ever seen was on Jura - they were basking on every other rock -or so it seemed at the time....
I take it you are not aware that Adders are protected, any disturbance including KILLING them is a criminal offence and totally illegal.
Well done for pubicly admitting it on an open forum.