You can regrow bok-choy from the stump. It's easy, and it's free food!
Just leave four or five centimetres of each stem on the base, and place the base in a container with one or two centimetres of water in the bottom.
The leaves will appear to grow out quite quickly.
After a few weeks it will either die or put out roots.
If it puts out roots, plant it in a pot. Or in the ground. Wherever you can plant things.

Once I tried this with iceberg lettuce. It didn't put out roots, and I haven't tried again, but I think it would work.

It's also easy to grow beetroot tops and harvest the young leaves for salad greens. Put them direct into some soil, just snuggle them in a little, no need to cover them all up.

(All photos on this page were taken by me.)