Mix apple cider vinegar with water and add the mustard seeds. Allow to soak for 2 to 3 days. The seeds will devour almost all the liquid. Beat the mixture with a blender, along with the rest of the ingredients until you get a smooth consistency. If you decide that it is too thick, add 2 tbsp water at a time and continue beating until smooth. With a spoon transfer the mustard in a jar, being careful not to let any air bubbles. Store it covered in the refrigerator. Mustard stand in the refrigerator to several months, but it is best to consume early opportunity.