Try this delicious cake recipe:
Grind mustard seeds as finely as possible in a cutter or coffee grinder. Caution: The mustard flour should not become warmer than 30 °C, so grind at intervals if necessary. Mix the resulting mustard flour with sugar, wine vinegar, salt and red wine and stir well, preferably in a hand mixer. Pour into a clean jar with a screw cap. At first, this paste is still quite liquid, but the mustard flour swells and the mustard gets the right consistency.
After about a day, season with gingerbread spice and pepper, steep for at least another week.
Can be kept in the refrigerator for about six months.