This recipe makes about 6 oz. and can easily be doubled.
Mix mustard seeds and mustard powder together, add water and let mixture sit for 30 minutes. Add vinegar and salt and mix well. Mustard will be spicy. Let sit in a cool dark place for 24 to 72 hours; the longer it sits, the milder it will get. Once at desired heat level, refrigerate. It will last several months, sealed, in the refrigerator.
Spicy: Use regular or hot mustard powder in place of mild, use more brown and less yellow mustard, or use crushed black mustard seeds in place of brown for more heat.
Maple Chipolte: Add 1 oz maple sugar and 1 tsp ground chipolte. (May need to add more water for desired consistency.)
Honey Mustard: Add 1 oz honey powder. (May need to add more water for desired consistency.)
Garlic Pale Ale: Replace vinegar with 4 oz of your favorite pale ale beer and add 1/4 tsp dehydrated roasted granulated garlic. (Recipe #565)