Mix in the wet ingredients including olive oil. It may seem runny but will thicken as it sits and once refrigerated.
Cover and store at room temperature for 2 days to allow the mustard to thicken and become less harsh. Allowing the mustard to sit at room temperature mellows the bite. The longer you allow it to “age” the more mellow it becomes.
Once the mustard is of the desired pungency, transfer to a clean glass and refrigerate covered tightly.
Will keep for up to 2 months refrigerated.