I also plan to make Brad Leone's recipe for mustard, which has Verjus instead of wine:

6 Tbsp brown mustard seeds
5 Tbsp yellow mustard seeds
1 Tbsp yellow mustard powder
1 Tbsp Kosher (or Sea) salt – Brad used 2 Tbsp
1/4 cup apple cider vinegar
1/4 cup Verjus
5 Tbsp sauerkraut juice

Combine mustard seeds together and process in spice grinder or coffee grinder until desired texture is reached. Pour into bowl with mustard powder and salt, and stir to combine.

Mix vinegar, Verjus, and sauerkraut juice in a one-cup measuring cup. Combine with mustard mixture and stir until completely mixed.

Pour into a one pint jar with a lid and store for 4 days at room temperature or up to a week, for a milder flavor.

Brad's note: if you use cold liquid ingredients, the mustard will be spicier, but if you use warm liquids, it will be milder.

I have zero experience making mustard so take this FWIW. My bottle of Grey Poupon lists “spices” genetically, and the recipe in my mustard book calls for allspice, white pepper, mace, turmeric and cinnamon. Plus Worcestershire. You might not want all of that, but it leaves me wondering if your recipe is a bit light.

Had to look up verjus, sounds like something I’d enjoy trying. Not cheap! Do you have a favorite brand/source?

I make the mustard recipe that is on the side of the can of Coleman's Mustard powder......
awesome stuff!!

I did find these recipes here:

Pete Hitchen's Blue\-Ribbon Beer Mustard
1 c dark beer
1/4c yellow mustard seeds
1/4 c brown mustard seeds
1\-1/2 c apple cider vinegar
1 small onion, chopped
6 cloves garlic, minced
1/2 c mustard powder
2 T. ice water
1\-1/2 tsp salt
2 tsp sugar
1/2 tsp ground allspice
1/2 tsp ground cumin
1 tsp grated fresh ginger
Pour beer over the mustard seeds and let soak overnight. In a non\-reactive (glass or stainless) pan, place vinegar, garlic, and onion. Simmer until liquid is reduced by two thirds. Strain and chill. Mix dry mustard and ice water and let sit for 20 minutes. Stir in cold vinegar, salt, sugar, allspice, cumin, ginger, and soaked mustard seeds. Place in a blender container and blend until mustard seeds are coarsely ground, scraping sides often. Pour into a saucepan and simmer over very low heat 10\-15 minutes, until it thickens. Cool, place in a glass jar with a tight lid, and let sit in a dark cupboard for 4\-5 weeks before using. Refrigerate after opening. Makes about 1 pint.

Homer Mayo's Horseradish Mustard

1/2 c mustard powder
1/2 c hot water
1/2 c white wine vinegar or rice vinegar
2 tsp salt
1 T. prepared horseradish
2 cloves garlic, finely minced
1 tsp sugar
1/8 tsp black pepper
1/8 tsp ground allspice
additional vinegar, if necessary

Mix the dry mustard and water and let stand for 20 minutes, stirring
once or twice. In a blender container, combine the vinegar, salt,
horseradish, garlic, sugar, pepper, and allspice. Process until the
garlic and horseradish have been pureed, then strain through a
fine-meshed strainer, pressing out the juice from any pulp in the
strainer. Discard the material in the strainer. In the top of a double
boiler, combine the strained liquid with the mustard-water paste. Cook
over simmering water for about 5 minutes, until the mustard has begun to
thicken (it will continue to thicken as it cools). Remove from heat and
allow to cool. If the mustard is too thick, thin it with a few drops of
additional vinegar. Place in a glass jar with a tight lid, and let sit
in a dark cupboard for 4-5 weeks before using. Refrigerate after
opening. Makes about 1/2 cup.

which use extra spices, but I'm not sure I want extra flavors. I think maybe those could be added later. I know I don't want cumin in my mustard, but maybe allspice is a good addition.

I made a very small batch of Brad's recipe. Here are the ingredients I used:

1-1/2 Tbsp brown mustard seeds
1-1/4 Tbsp yellow mustard seeds (1 Tbsp + 2/3 tsp)
3/4 tsp yellow mustard powder
1/2 Tbsp sea salt
1 Tbsp Pasolivo Winter Aprobsia vinegar* (Brad used apple cider vinegar)
1 Tbsp Verjus
3-1/2 tsp sauerkraut juice

*Ingredients in this vinegar: vinegar, pears, apples, mulling spices. It has a mildly sweet flavor, and I thought it would be a better substitute than white wine vinegar. I do not have any apple cider vinegar, even though I have many different kinds of vinegar. I have distilled vinegar, but it has no flavor.

I was going to use less salt because people on Youtube said that the mustard came out too salty for them, but when I tasted the mixture, it was extremely bitter with a reduced amount of salt, and so I put in the full amount, which seemed to help. I know you are not supposed to taste it at this point, but I was still a bit curious. If it comes out too salty, I can reduce the salt in the next batch. I think my batch produced about 1/3 cup of mustard. It should be ready for me to taste test it by Saturday.

This small batch of mustard came out very good, and I have moved it to the refrigerator, as it is mild enough for me now and almost used up. I plan to make a larger batch of this soon.

Yesterday, I started on this Dijon mustard recipe:

Ingredients for four (8-ounce) jars of Dijon:

1 yellow onion, chopped
2 garlic cloves, minced
1-1/2 cups white wine
2/3 cup white wine vinegar
1 cup yellow mustard seeds (I used 1/4 brown mustard seeds)
1/4 cup dry mustard (I used Indian yellow mustard powder)
1 teaspoon salt
1 tablespoon garlic powder
1 cup water, plus more as needed

Add chopped onion, garlic, wine, 1 cup water, and vinegar to a saucepan and bring to a boil. Reduce the and cook for 15 minutes. Allow to cool off heat.

Strain out onion and garlic and discard or save for other use.

Add mustard seeds, dry mustard powder, salt, and garlic powder to strained liquid. Allow to sit for two days, covered. (This is where I am now.)

Pour mixture into a blender and blend until smooth, or use a stick blender. Remove to a saucepan and cook on medium heat for 10 minutes, adding water as needed to maintain the correct consistency.

Put in jars and store in the fridge for one week before using.

----------------

I cut this recipe in half, as it seems reasonable enough, but I did use 1/4 brown mustard seeds, as I found other recipes with as much as half brown mustard seeds. Otherwise, I have followed the recipe as I found it. I plan to cook only half of it and save the other half without cooking for a week or two to see how it tastes without cooking. If I don't like it, I can always cook it later, I think. I'm not sure it needs the final cooking, which I think will make it more mellow, and I may or may not prefer that.

I sampled the Dijon style mustard yesterday, and it was a bit of a disappointment. I brought the cooked half of the recipe with me, along with my last batch of sauerkraut, and made Reuben sandwiches for lunch. The mustard tasted okay on the sandwiches, but tasting it out of the jar was not so great. I may give up on trying to make Dijon mustard and just buy Grey Poupon instead. Brad's mustard recipe was great, and so I will continue to make that. I do like Brad's mustard better than Grey Poupon. I'll check the uncooked mustard when I get back to L.A. I think part of the problem is that it needs more salt. Brad's recipe has much more salt than the Dijon recipe I used. Grey Poupon also has a high salt content.

These all look good, my family are all mustard fans