Make the salsa verde by putting 10 anchovy fillets, 15 basil leaves, 15 mint leaves, the leaves from a small bunch of flat-leaf parsley, ¼ tbsp Dijon mustard, 1 chopped garlic clove and 1 tbsp capers (rinsed) in a food processor. Pulse-mix, adding the lemony olive oil as you do so (while holding back the lemon slices). Scrape into a bowl.