A hand-held blender can be used to make this mustard with bite. Add more tarragon, if preferred. The oil helps preserve the mustard.
- Place the peppercorns, salt, tarragon and turmeric in a blender. Mix until smooth. Pour into a large bowl.
- Add the remaining ingredients to the blender and mix until well combined. The mustard seeds should still have some shape.
- Pour into the bowl and mix well.
- Stand overnight to thicken. Pour into small jars and seal. Keeps for at least 6 months in a cool place.