I've been working on a honey-whiskey based recipe for a couple of years now. Finally getting close to a flavor blend we really like. The flavors of the honey and whiskey will need to be tweaked if you use Jack Daniel's or other spirit. This is a yellow mustard with dark flecks and is moderately sweet. If you want the mustard to have more kick, shorten the mellowing time. Less time at room temp = more heat.
If you use onion, be careful to keep the vinegar content reasonably high to minimize the chance of microbial growth. Speaking as someone who got food poisoning 3 times from eating someone else's tainted mustard (took me awhile to figure it out, much to my misery), it does happen and it's worth being careful about.
Dee's Honey Rye Mustard
Whole yellow mustard (Penzey's) ... 60 g
Cracked brown mustard (Penzey's) ... 20 g
Water ... 1/2 cup
Rye whiskey (Templeton) ... 1/2 cup
Apple cider vinegar (real!) ... 1/2 cup
Honey (Dee's bees) ... 1/2 cup
Turmeric (Penzey's) ... 1/2 tsp
Kosher salt ... 1/2 tsp
Mellowing time ... 3 days
Place mustard seeds, water, vinegar, and rye whiskey in a small bowl. Cover and let soak at room temperature for the mellowing time (3 days).
Stir in honey, turmeric, and salt. Transfer mustard mixture to the "twister" jar of Blendtec blender. Do not overfill the blender jar -- about 1/3 full is enough! Process until smooth enough to suit. The "whole food" juicing cycle seems to work well.
Mustard will seem too thin at first, but will tighten up with time. Transfer to an airtight container and let rest in refrigerator for 1 to 2 days before use. The mustard heat will gradually mellow with time. If the mustard gets too dry, stir in a little water to loosen. Keep refrigerated.