I grew up with Boetje’s so that’s what we use other than the occasional plain yellow mustard. We’ve tried other coarse ground mustards but they just don’t have the flavor we like. http://www.boetjesmustard.com/
Interesting - my experience doesn’t match that, but I’m not going to dispute those results.
It may vary with the type and particle size of the ground mustard (mine is usually coarse). IMO, next day is not discernibly ‘off peak’ for heat, and incidentally allows enough time for development of the ‘non-heat’ flavours.
I have a cookbook with a recipe for Friesian Mustard Soup. It’s a seafood chowder in a mustard cream base. You can really savor the mustard, and it never lasts long around my place.
Dang, now I want some.
For what it’s worth, it’s dead easy to make yourself. Penzey’s will sell nearly a pound of brown mustard seeds for under $13.50. Yellow seeds are a little over a pound for the same price.
Some salt, vinegar and flavorings are all you need to make some amazing mustard at home.
The bags mentioned above are 3 cups, which hydrate to 3-4x their volume. I’ve re-hydrated in beer, wine or just straight vinegar. All give slightly differences in flavor. Once hydrated, put it in a blender and whiz it up until it’s the texture you want.
Add salt to taste, add flavorings to taste (onion powder, garlic powder, herbs, cayenne, any or all). Add more vinegar or other liquid to get it to the consistency you want. Add mustard powder (or more seeds) if it’s too thin or want more mustard flavor/heat.
As long as I’m using a high proportion of vinegar, I can any that I don’t want to store in the fridge with a simple hot water pack. Clean mason jars into my canning pot, process at a boil for 20 minutes.
That’s what I was going to mention, too! I don’t eat a ton of mustard (mostly on the fancy sandwiches I make every couple of weeks), so a jar lasts me a long time–but Lusty Monk mustard is my go-to mustard.