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.