1/2 cup plus 3 tablespoons yellow or brown mustard seeds
About 1/4 cup plus 2 tablespoons (1 1/4 ounces) mustard powder
1/2 cup Gravenstein Apple White Balsamic vinegar from The Mighty Olive
1/2 cup flat hard apple cider
1 1/2 teaspoons kosher salt
1 Granny Smith or Gravenstein or similar tart apple, peeled, cored and finely grated
Soak the mustard seeds: Place the mustard seeds and powder in a medium glass or ceramic bowl along with the balsamic and hard cider overnight. Place the mixture in a food processor along with the salt and process for 1 to 2 minutes until the seeds are coarsely ground. Add the grated apple and pulse a few times to incorporate. This makes about 1 2/3 cups mustard.
The mustard will be very pungent at first. Cover and refrigerate for a few days (or to taste) before using.