Crush the mustard seeds in a mortar pestle or a coffee grinder (it’s okay if they’re coarsely ground).

Chop the carrots and beet into long pieces.

Combine all the ingredients in a glass jar (I use a half-gallon mason jar) and cover with a lid or cheesecloth.

Let the jar sit in a sunny spot for at least one week - stirring with a wooden spoon daily.

Once the kanji develops a tangy flavor, that means the drink is fermented.

Strain the drink, save the pickles to enjoy later.

Put the drink in the refrigerator to chill.