Ingredients:
3 cups white wine
2 cups water, or more as needed
1 ⅓ cups white wine vinegar
2 yellow onion, chopped
4 cloves garlic, minced
2 cups whole yellow mustard seeds
½ cup dry mustard
2 tablespoons garlic powder
2 teaspoons salt
8 1-pint canning jars with lids and rings
Directions:
Combine white wine, water, vinegar, onion, and garlic in a saucepan; bring to a boil, reduce heat to medium low, and simmer until flavours combine, about 15 minutes.
Cool to room temperature and pour through a strainer into a large bowl; reserve liquid and discard onion and garlic.
Stir mustard seeds, dry mustard, garlic powder, and salt into strained liquid; cover the bowl with plastic wrap and let sit at room temperature until mixture thickens, 24 to 48 hours.
Purée mustard mixture to desired consistency using a stick blend.
Transfer mustard mixture to a saucepan and add enough water to reach a smooth consistency. Bring mustard to a simmer, reduce heat to medium, and cook, stirring constantly, until flavours combine, about 10 minutes.
Pack mustard into hot, sterilized jars, filling to within 1/4 inch of the top. Run a knife or thin spatula around the insides of the jars after they have been filled to remove any air bubbles.
Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with the lids and screw on the rings. Refrigerate mustard until flavours blend, at least 1 week.
borrowed from: https://www.allrecipes.com/recipe/240790/chef-johns-dijon-mustard/