Step 1

Pour both yellow and brown mustard seeds into a small mixing bowl or measuring bowl and pour vinegar and beer over. Whisk together to blend and cover the mixture with plastic wrap. Set aside on the countertop for 12 hours until the liquid has been absorbed.

Step 2

Pour soaked seeds into a food processor with the remaining ingredients. Pulse several times to mix then process for a minute.

Step 3

Pour mixture into a sterilized glass jar and refrigerate. Let rest and mellow for 2 weeks in the fridge before using. The mustard will keep for up to 6 months covered and refrigerated. This makes about 1 1/2 cups.