Combine Yellow and Brown Mustard Seeds and Ground Yellow Mustard in a small bowl and set aside.
In a medium saucepan, combine remaining ingredients. Simmer on medium-high 10-15 minutes, or until reduced by half.
Pour this mixture into the bowl with the mustard seed mixture and let soak for 24-48 hours at room temperature. You may need to add vinegar if it soaks in. The liquid should be enough to cover the seeds.
Place mixture in a food processor or blender and process until smooth. It will thicken upon standing.
Place mustard into jars, and let age for 3 days. If mustard becomes too thick, just add vinegar in small amounts until desired consistency.