In a non reactive pot or jar, combine mustard, vinegar, beer, pepper, and garlic. Cover and soak for 36 to 48 hours; adding additional vinegar and beer, in equal proportions, in order to maintain enough liquid to cover seeds.
Puree mixture with cumin and Tabasco sauce in a food processor.
Process until mixture becomes creamy and flecked with seed, about 3 to 4 minutes.
Add additional vinegar as necessary to create a creamy mustard.