Finely cut the chives.
Mince the garlic with a pinch of salt using the back of the knife.
Whisk together the vinegar, the egg yolk, Dijon mustard and garlic.
While continuously whisking the egg yolk mix drizzle in the oil little by little, until you obtain a thick and glossy mix.
Stir in the grainy mustard and taste for seasoning. Finish with the chives.
«This dipping sauce will keep for up to three days in the refrigerator.»