There is an article in the La Times about mustard. Here are 2 of the recipes. Second one sounds like it would be great with the addition of some habs! Would it keep longer with additional vinegar?

The Seed of a Bright Idea By John Ash

The most basic of mustards is simply a mixture of mustard powder and water. This recipe has a little more going for it. Remember that most homemade mustards tend to be a bit more runny and more pungent than commercially made, but that's their charm. Also, homemade mustard needs to mature at least a day, and preferably longer, before being used. When it's first made, the flavor will be almost unpleasant. Coarsely grind yellow and brown mustard seeds in spice grinder or coffee mill. Mix together with mustard powder and water. Allow mixture to stand at least 1 hour. Stir in vinegar, brown sugar and salt. Cover and refrigerate at least 1 day before using.

1 cup. Each tablespoon: 41 calories; 148 mg sodium; 0 cholesterol; 2 grams fat; 4 grams carbohydrates; 2 grams protein; 0.50 gram fiber.