To get started, you'll need to grind the mustard seeds. You can grind them by hand the old-fashioned way, using a mortar and pestle, for a bit of an arm workout! Or, use a spice grinder to make the process faster.
Once the spices are ground, transfer to a glass storage jar and add in the rest of the ingredients. Stir well to mix.
For best flavor, allow the mustard to sit at room temperature for up to 8 hours before storing in the fridge. (You can actually let the mustard "cure" for a few days on the counter, if you like, but I haven't tried it myself.)
If the mustard has a little too much "bite," try adding a bit of honey or coconut crystals to balance the flavor.
The mustard flavor will get better with time, so it's best to make homemade mustard a few days before you plan on serving it.
Store in the fridge, and use it to make your favorite sandwiches and salad dressings!
The more finely ground your mustard seeds, the more potent and spicy the flavor will be. For a more mild mustard, try soaking the seeds whole, with the rest of the ingredients, then briefly pulsing in the food processor for a chunkier whole grain mustard. Instead of water, you can use white wine, beer or apple cider for a more complex flavor. I recommend apple cider vinegar or coconut vinegar because they are less acidic and yeast-feeding than traditional vinegars, but any type of vinegar can be used to make mustard. Feel free to add any herbs you like, such as fresh dill. For a spicier mustard, try adding a bit of horseradish or garlic. For a honey mustard, try adding a 1/4 cup of honey.