1/4 c Black mustard seeds
1/4 c Yellow mustard seeds
1/4 c Dry mustard powder
3/4 c Cold water
1/4 c Dry white wine
1/4 c White wine vinegar
1 teaspoon Dried tarragon
1/8 teaspoon Ground allspice
Mix mustard seeds, powdered mustard, and water in the upper pan of a non-corrosive double boiler. Let stand at least three hours.
In another non-corrosive saucepan, mix the wine, vinegar, tarragon, and allspice and bring to a boil. Strain the liquid into the mustard mixture and blend well.
In the lower pan of the double boiler, heat water to boiling, then reduce heat to a simmer. Place the upper pan, containing the mustard mixture, on top. Cook, stirring, until the mustard is as thick as you like. It will thicken a bit more as it cools. Cover and refrigerate.