Place the mustard seeds in a container with the Chambord and red wine vinegar and leave to soak for at least 72 hours. The seeds will swell as they absorb the liquid so ensure you choose a container big enough to allow this
Transfer the mixture to a blender and blitz to your desired consistency
Add the raspberries to the blender and blend again until incorporated
Taste the mustard and add more of any of the ingredients, according to your preferences
Store in an airtight container in the fridge for up to a week. If you want to store the mustard for longer, omit the fresh raspberries and blend them in before serving
