Add brown and yellow seeds, water and garlic cloves to bowl of a food processor or blender. Puree until mixture thickens up, which may take anywhere from one to 10 minutes depending on the power of your blender or food processor.
Add mixture to mixing bowl.
Mix in mustard powder. To achieve a mellower/less spicy mustard, wait 10 minutes before adding remaining ingredients.
Add salt, turmeric, honey and acidic liquid (brine, kombucha or whey) to bowl and mix well.
Dispense mixture into a wide mouth pint or larger jar.
Tightly secure lid and ferment at room temperature 2 to 4 days. The mixture will continue to thicken up for a day or so as the mustard powder absorbs the liquid.
Store in refrigerator for up to a year.