½ cup dry white wine, such as Sauvignon Blanc or Chardonnay
½ cup white wine vinegar
¼ cup brown mustard seeds
¼ cup yellow mustard seeds
½ tsp kosher salt
Instructions
Place all ingredients in a small glass bowl. Stir to fully incorporate and cover tightly with plastic wrap. Let sit at room temperature for 2 days.
Remove the plastic wrap and transfer contents to a blender (an immersion blender also works very well). Blend for approximately 30 seconds or to desired consistency.
Transfer the mustard to a sterilized, small glass container with a tight fitting lid. May be kept refrigerated for up to 3 months – the longer the mustard sits, the less spicy it will become.
Recipe by at https://hapanom.com/coarse-ground-mustard/