mustard seeds, black
apple cider vinegar
In a small bowl, combine mustard seed and dry mustard.
In a 1- to 2-quart non-aluminim pan, combine remaining ingredients.
Simmer uncovered, on medium heat until reduced by half, 10- 15 minutes.
Pour the mixture into the mustard mixture.
Let mixture soak at room temperature 24 to 48 hours, adding additional vinegar if neccesary in order to maintain enough liquid to cover seeds.
Process the seeds and mixture in a blender or food processor until puréed to the texture you like --this can take at least 3 or 4 minutes.
Some prefer whole seeds remaining, others a smooth paste.
The mixture will thicken considerably upon standing.
If it gets too thick after a few days, stir in additional vinegar.
Scrape mustard into clean, dry jars; cover tightly and age at least 3 days