I got this from this month of Mens Health, Its called Harbour Guinness Mustard.
What you need:
2 Small Shallots
1/2 tsp Vegetable Oil
1 Cup Mustard Seed
1 Can Guinness Draught (or your own wold be better)
Slice the shallots and saute them in oil. Add the mustard seeds and stir over low heat for 30 seconds. Add enough beer ro barely cover the seeds, and simmer until seeds become tender. Let the mixture cool, and then puree it in a blender. Add more beer as necessary to adjust the consistency. Keeps up to 6 months in the fridge.
Thought this looked good, im sure all the mustard lovers out there will like this one.