Meanwhile, make the salsa verde. Put the anchovies with a teaspoon of their oil, capers, garlic, a pinch of salt and the half the herbs, in a mortar and pound with a pestle until a paste has formed. Stir in the mustard and vinegar. Loosen with a little oil, then stir in the rest of the herbs. Mix well to your preferred consistency. Taste and adjust the seasoning as necessary.