Soak the Mustard Seeds. In a small bowl, combine the brown mustard seeds, yellow mustard seeds, and white wine. Cover and let the seeds soak for 24 hours at room temperature. This step softens the ...

(The mustard seeds will soften and soak up most of the beer.) Sterilise the jars for the mustard. Wash in very hot water or on the hot cycle of a dishwasher. Preheat the oven to 160C/325F/Gas 3.