For more than 20 years, I’ve been making my own. I started around the same time I began brewing my own beer. I was old enough to buy mustard; not so much the beer. Sure, I still buy unusual or specific mustards — moustarde au violette, creole, Scharfersenf, or Dijon — but whipping up a batch of perfectly respectable homemade stuff is fast and cheap. It’s also so easy that I often make it just by eyeballing ingredients.
Here’s my eyeball method for making our house mustard: pour an equal measure of yellow and brown mustard seeds in a large jar (maybe a little heavy on the brown seeds). Cover with two fingers of cane vinegar and let the whole mass soak. If the seeds are particularly thirsty, top off with more vinegar the next day. After 3-5 days, transfer to a blender (or use an immersion blender), then add mild mustard powder, a bit of salt, and a few tablespoons of honey. Blend to crush the seeds lightly. Store in clean glass jars. It’s ready to use as-is, but benefits from a few days’ rest.
If you’re more comfortable with specifics, try this:
Rowley’s House MustardYou can store this mild mustard at room temperature in the cupboard or pantry, but the coolness of a fridge seems best to preserve its fugitive bite.
½ - ¾ cup black/brown mustard seeds
½ cup yellow mustard seeds
1 - 1½ cup Filipino cane vinegar
½ cup yellow mild mustard powder
1 Tbl salt
3-4 Tbl honey
Soak mustard seeds in vinegar 3-5 days. Add remaining ingredients and blend the whole mass in a blender for 5-12 seconds until the seeds are lightly crushed. Store in clean glass jars.