Pour the soaked seeds and liquid into a blender or food processor. Add salt, honey, turmeric, and pepper.
5 Process to desired texture
6 Blend until it looks right to you. For a rustic Dijon-style mustard, leave some grain. For a smoother mustard, blend longer and add 1–3 tbsp water as needed.
7 Taste and adjust:
8 It will taste very sharp at first. Adjust with:
9 More salt if it tastes flat
10 More vinegar if it needs brightness
11 More honey if it is harsh
12 More water if too thick
13 Rest before serving
14 Transfer to a jar and refrigerate at least overnight. It gets better after 2–4 days.