Wash the celery and remove its coarse longitudinal fibers (similar to beans). Divide lengthways into two or three strips and cut off small pieces.
Heat the oil in a saucepan and sweat the celery pieces. Dust with broth and pour water over it. Then cover and simmer for a few minutes.
Just before you think the pieces are okay for you, put the nut butter on the vegetables and let them melt for a few minutes with the lid closed and reduced heat. Sprinkle with the coriander and stir vigorously. Possibly season to taste.
For me this is a main course, as a side dish it could be enough for two people.
Note: A sauce is not great here. If you want more liquid, simply double the water and possibly stir in more nut butter. Just try.