Guinness Mustard

In a nonreactive container, combine mustard seeds with beer and vinegar. Let sit 48 hours. Check periodically to make sure seeds are covered by liquid; add more if necessary. 

Transfer seeds and liquid to a blender or food processor. Add remaining ingredients. Process until seeds become creamy, 4 to 6 minutes. 

Store in an airtight container in the refrigerator for at least 1 week before using to let the flavors develop. The mustard will keep for up to 1 month.