1. In a small bowl, mix together the salt, vinegar, and shallot. Let stand for about ten minutes.
2. Mix in the Dijon mustard, then add 3 tablespoons (45 ml) of olive oil. Stir well, then taste. If too sharp, add the additional olive oil and more salt, if necessary. Romain said one needs to add beaucoup de mustard, so feel free to add more as well.