Step 1

Cook the egg in boiling water for 10 minutes. Remove from heat, drain away the water, and cool the egg by adding ice and cold water to the pot.

Step 2

Once cool, peel the egg then extract the yolk. In a medium-sized bowl, mash the yolk until smooth with the mustard.

Step 3

Dribble in the olive oil, beating with a fork or wooden spoon while doing so (trying to make an emulsion), then adding the vinegar.

Step 4

Chop the egg white and cornichon separately into fine cubes, the size of the capers, and add them to the sauce. Then add the capers themselves.

Step 5

Stir in the herbs and add salt and pepper. Taste, and season with additional salt, pepper, and vinegar, if necessary. Serve at room temperature.