Homemade Horseradish Mustard
- Stir together the dry mustard and water and let stand, uncovered, for 20 minutes, stirring once or twice.
- In the container of a blender or a food processor, combine the vinegar, salt, horseradish, garlic, sugar, peppercorns, and allspice.
- Process until the garlic and horseradish have been pureed in the liquid, then strain through a fine-meshed strainer, pressing all juice from any pulp in the strainer.
- Combine the strained liquid with the mustard-water mixture in the top of a double boiler set over simmering water.
- Cook, stirring constantly, for about 5 minutes, or until the mustard has thickened (it will thicken more while cooling).
- Cool and taste.
- Add more prepared horseradish, if desired, and if the mustard seems too thick, thin it with a few drops of white wine or additional vinegar.