1 large bunch fresh flat-leaf parsley
1 bunch fresh basil
a handful fresh mint leaves
3 garlic cloves, peeled
100 g (4 oz) salted capers, drained and rinsed
100 g (4 oz) anchovies, prepared (see here)
2 tablespoons red wine vinegar
5 tablespoons olive oil
1 tablespoon Dijon mustard
Maldon salt and freshly ground black pepper
Using a food processor, pulse-chop the parsley, basil, mint, garlic, capers and anchovies until roughly blended. (This sauce may be prepared by hand, on a board, preferably using a mezzaluna.)
Transfer to a large bowl and add the vinegar. Slowly pour in the olive oil, stirring constantly, and finally add the mustard. Check for seasoning.