This recipe is really simple, and tastes even better than the mustard I was buying at the shop.
6 tablespoons whole mustard seeds (I used all yellow this time. If you add some brown seeds to it, it will be spicier)
1/3 cup water
2 tablespoons apple cider vinegar
1/2 teaspoon salt
Mix all the ingredients together in a ceramic or glass bowl. Cover and refrigerate overnight.
Add 3-4 tablespoons more water and grind in a food processor or mortar and pestle until it’s the consistency you want. Add extra flavourings if you wish (or some turmeric if you want it to be bright yellow), transfer to a glass or ceramic jar and store in the fridge. It will keep for a few weeks this way.