As the dried cranberries soak with the mustard and vinegar, their bright red color leaches out into the vinegar. The resulting mustard is a pretty, cranberry-tinted pink.
In a non-aluminum pot or jar, combine the mustard seeds, vinegar and cranberries; cover and soak for 48 hours, adding additional vinegar if necessary to maintain enough liquid to cover the seeds.
Scrape the soaked seed-and-cranberry mixture into a food processor and process until the mixture turns from liquid and seeds to a creamy mixture flecked with seeds and bits of cranberry. Add honey and salt.
The process takes at least 3-4 minutes, so be patient. You may need to add additional vinegar as necessary to create a nice creamy mustard; keep in mind that it will thicken slightly upon standing.
After about one week of aging, the cranberry flavor seems to settle into this mustard and make it all the better, but it is perfectly good immediately.
Makes about 3 1/3 cups.