In a 1 quart glass container with a tight fitting lid, stir together all of the ingredients and then refrigerate for 30 days.
After 30 days, scrape the mustard into a bowl of a food processor and purée it for 5 to 10 minutes, or until it reaches the desired consistency. It’s best to process the mustard in 2 to 4 minute increments and let the food processor rest for a few minutes between to prevent overheating.
The mustard is ready to use immediately or can be stored in an airtight container in the refrigerator for up to two months.