A dry mustard is when the mustard seed is ground up (may also be called ground mustard or mustard powder).
Mustard seeds are the small round seeds that come from several different types of mustard plants. The seeds are approximately 1-2 mm in diameter and the seeds are also known as fruit pods. Mustard seeds are harvested from three different plants: white mustard (better known in this country as yellow mustard), brown mustard and the very hard to find black mustard.
Making your own prepared mustard is easy! Pour the mustard powder into a bowl and add enough vinegar, wine or beer to completely cover the powder (our rule of thumb is about ¼ cup of ground mustard to 3 tablespoons of liquid). Let sit for about 20 minutes and then add in other spices and herbs and mix into a smooth paste. If you’re looking to maximize the heat level, then mix the ground mustard with a very cold liquid. If you want a milder mustard flavor, mix with a hot liquid. If you do decide to use some whole seeds, dry roasting these will enhance both the aroma, as well as intensifying the flavor. The end flavor of your mustard will ultimately depend on the type of liquid that you mix your mustard with. Vinegar will give you a small tang, wine a spicier pungency and beer a more extreme heat. Water provides the strongest flavor, but will not stop the enzyme’s activity, and therefore does not make a stable mustard (meaning water produced mustard has a shorter shelf life).
You may need to add a bit more liquid depending on how much additional seasoning you add. Mustard is fun! Try adding whole mustard seeds for a whole grain mustard, horseradish powder for horseradish mustard, or honey for honey mustard! The possibilities are endless! Try adding other spices and herbs as well. I personally love tarragon and/or paprika in my homemade mustard!