In a medium bowl, combine the mustard seeds with the Rye Festbier (or malty beer of your choice) and vinegar. Mix well, cover and refrigerate overnight. This allows the seeds to soften and absorb the flavors of the beer.

After soaking, transfer the mustard seeds and any remaining beer to a blender or food processor. Add the brown sugar, maple syrup, and salt.

Blend the mixture until it reaches your desired consistency. For a coarser mustard, blend for a shorter time; for a smoother mustard, blend longer.

Transfer the mustard to sterilized jars and seal tightly. For the best flavor, let the mustard sit in the refrigerator for at least a week before using. This allows the flavors to meld and develop.

Use your homemade beer mustard on sandwiches, with pretzels, as a marinade for meats, or as a flavourful addition to any dish.