Pignuts. Tasty, crunchy morsels. Considered a famine food now really, but if you're clever about it, easily found and worth the effort. I grow some in pots. It's much easier emptying out a pot than it is trying to find a dog piddle free zone where they're growing profusely enough to dig up and gather without taking too many. The seeds are abundant though, and if you scatter them (left too long, mine self seeded among the gravel around the slabs ) in good light in among dampish clear gravel or soil, then they'll come up easily for you. It's only the start of January, yet mine are already showing their first leaves in the path, and they are just visible in the woods too. Tiny wee things looking almost like fine parsley. These have sprouted from last year's nuts.