Very simple to make......make your own because almost all store bought mustards are not wheat and corn free even when they say gluten free. Vinegar is normally made from wheat or corn or some other troublesome grain. The containers are normally plastic also which can leach chemicals into the prepared mustard so....on to the recipe. The author say that this recipe is similar to Frenchs yellow mustard. 

Update from heartweed: I made this and just to let ya know my mustard is still on the hot side 6 days later. Its that kinda hot that doesn't linger but goes straight up your nose for that sinus burn for a few seconds and then stops. Great for clearing the sinuses. I kinda like it! :)

Ingredients:

• 1/2 cup water
• 8 tablespoons dry ground mustard(cut in half next time? too hot) 
• 4 tablespoons apple cider vinegar
• 1 tsp. arrowroot powder (optional used as a thickener)
• 1/2 teaspoon plus 1/4 teaspoon sea salt
• 1/4 teaspoon turmeric (for color not necessary) 
• Pinch of garlic powder
• Pinch of paprika

Directions:

1. Combine all ingredients in a small sauce pan.  Whisk to combine.
2. Heat until boiling.  Simmer on low for 10 minutes or until sauce has reduced to the thickness you would like it.  Stir frequently.
3. Store in jar in fridge for up to a month.  For a more mellow mustard, allow to sit for a few days to become less hot.

Notes:

• Mustard is hot when first made.  Let is sit for a few days and it will lose much of its heat. (in fridge with lid on)
• Makes about 1 cup.
• She also says that it last about a month in fridge , at least that is as long as it last hers before eaten. She wonders if it can be canned , so do I.
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