Chestnuts.

 

I just picked up what would fit in my pocket. It's Autumn so the Eastern walking track I use is smothered in fallen chestnuts. There are about 10 tress. Nobody else seems to pick any up because those who walk dogs won't go there when the prickly nuts are all over the ground (The prickles get in the soft pads on a dogs paw )

 Before they fall the nuts look attractive in the lime green prickly containers.

 Castanea ( not sure which variety ) probably Castanea sativa.

 As kids we used to roast them on a metal hearth shovel in the open fire till they split or exploded.

 As a nut it has no oil and a high starch content but tasty roasted with butter if you can be bothered.