This is napa cabbage that has been soil blocked. We started it in our germination chamber.
They are on tables in our unheated greenhouses right now and we will plant it out along with the other seedlings in the background - tatsoi, spinach, mizuna, dill - into our unheated greenhouse in about 2-3 weeks.
If you would like to learn more about soil blocking, go to this video which was made at our farm by the Sooke Region Museum