First, we must develop the brown butter. For this, it is convenient to use a small frying pan or saucepan with a light bottom, which allows us to observe how the butter changes color. It is enough to heat this over low heat between 5 and 10 minutes, observing how it slowly caramelizes. The brown butter is ready when a fine foam forms and, when stirred with a spoon, we see how it has reached a golden brown hue.
Once the butter reaches the right color, we must transfer it to a new container. In the process a solid waste deposit, which can be used or not in the vinaigrette, to obtain a more or less powerful flavor. We have chosen to add it.
Once we have the butter ready, we just have to mix three parts of this, with one part vinegar and one part Dijon mustard. With 50 grams of butter, about six tablespoons of brown butter come out, which is enough to add two tablespoons of vinegar and two of mustard.
Mix the basic ingredients in a food processor or mincer, along with a teaspoon of salt and another of freshly ground black pepper. We have also added a handful of fresh coriander, but this is optional, and other herbs such as parsley or chives can be added. Mix all the ingredients well and you will have the best sauce in the world to accompany meats and vegetables.
The ideal is use the sauce as soon as it is cooked, because as soon as the butter cools it solidifies and loses its creaminess. If we make it from one day to the next, it is best to keep it in the refrigerator to take it out at least an hour before we use it or (if we have forgotten) give it a heat stroke in the microwave.