Soak the Mustard Seeds
In a glass or non-reactive bowl, combine mustard seeds, 4 ounces of the vinegar, and all of the white wine.
Cover and let soak at room temperature for 24–48 hours.
(Longer soak = smoother, less bitter mustard.)
Blend
Transfer soaked seeds and liquid to a blender or food processor.
Add the remaining 3 ounces of vinegar, sugar, and salt.
Blend until smooth or slightly grainy, depending on preference.
Rest & Mature
Transfer mustard to a clean jar.
Let it rest in the refrigerator for 48 hours before using to mellow the sharpness.
