This is a very easy recipe and once you make a batch you can keep it for months. It also makes a wonderful gift around the holidays, or anytime! From Cooking with Caprial, American Bistro Fare cookbook. Cook time is standing time.
Place the mustard seeds and dry mustard in a spice grinder or blender and blend until the seeds are broken up. A coarse grind gives the mustard some texture. Place the ground mustard seed and dry mustard in a bowl and pour the water over the top. Stir and cover. Let the mixture stand for 4 to 5 hours, stirring a few times.
Put the mixture in a food processor and add vinegar, honey, sugar, salt, pepper, basil, thyme, rosemary, and sage. Puree until it's smooth. If mustard seems too dry, add warm water to make a smooth paste. Store in a jar at room temperature until the mustard mellows to your taste, up to 2 weeks for a very mellow mustard. Enjoy!