A suggestion made by Anna has prompted me to think what we can learn from random gardening mistakes, or shall we say, unplanned activity.
I use a lot of salad vegetables and always have a variety of leaves growing to use as a base for additional ingredients. I sow a selection in various seed trays, which I then prick out and later plant into the garden. A few years ago, at the tail end of the summer, I sowed seeds into their seed trays as usual. For whatever reason, I failed to prick out and then felt it was too late to do anything much with them, so I was left with several seed trays full of fresh young seedlings. And I left them. But what happened then was that they provided me with a steady supply of cut-and-come-again salad leaves (the kind you pay a fortune for in bags in supermarkets) to enjoy through the winter. Ever since then, I use this method to provide me with small young and tasty salad leaves, throughout both the summer and winter. I do this with Mizuna, Endive, Rapa da Foglia (turnip greens), mustard, rocket as well as the usual lettuce varieties which we grow. I am sure it works equally well with chard and beetroot and members will have their own varieties to suggest here. Obviously the mild winters we have been experiencing do help, I am not sure what a sharp frost would do. Ultimately, the plants will become very rootbound, but growth in the winter slows down, so this takes a while to happen.
Trays of seedlings sown 5 September.
The usefulness of this method is also that you could do this on your kitchen windowsill, balcony, or whatever space is available.