I’ve been self-sufficient in fresh vegetables year round and have blogged and lectured about how I can do this even in winter without a greenhouse, without a freezer and without using additional energy apart from my own manual labour :) The most important factor allowing me to do this is the cold cellar under the house where I can store vegetables cold and frost free. None of the common winter leafy green vegetables further south in Europe – kales (grønnkål), chards (mangold) and leek (purre) – can be reliably overwintered outside here, although winters are getting milder. For example, swiss chard is killed by the first hard frosts which due to our northern location last all day (little direct solar warming at this time of year). Usually I’m taken by surprise by hard frosts in early November and there’s a panic digging up vegetables and I often have to use an iron bar to get through the ice layer. Not so this year. Thanks to corona and a very mild first part of November, I’ve had more time for the harvest. Last week I lifted the swedes and turnips and yesterday the parsnips, jerusalem artichokes and carrots. Today, I moved all the swiss chards, celery and chicories (sikkori) to large buckets, planted in soil, ready to move quickly inside later in the week if necessary as colder weather is forecast. In the past I’ve stored these winter vegetables in hand made wooden crates filled with soil. However, after 20 or so winters, they’re no longer usable and I hadn’t got round to making new ones, so I will store in these large plastic buckets, which had been purchased to plant the Allium collection, now with a permanent home at the Ringve botanical garden. 
I’ve also been digging up perennial vegetables for winter forcing. This includes various onions – Allium senescens,  Allium flavescens, Allium angulosum and Allium cernuum.  In addition, I’ve dug a udo (Aralia cordata) root and also a few ostrich ferns (Matteuccia struthiopteris) and Hosta “Frances Williams” (sieboldiana). Finally,  I’ve been digging large amounts of my most important winter vegetable, dandelion! (see my 2018 harvest here: https://www.edimentals.com/blog/?p=20124)
19th November: the next morning it snowed (see the video at the bottom)!

Harvested swiss chards including the Lucullus type and perpetual spinach (all Beta vulgaris var cicla):

Chards with celeries at the beginning: