• 4 boneless, skinless blue-eye fillets (180g each)

• sea salt

• 1 tsp olive oil (plus extra, to serve)

• freshly ground black pepper

• 1 lemon, quartered, seeds removed

For the tarragon tartare sauce

• 2 tbsp cornichons, finely chopped

• 1 tbsp baby capers in vinegar, drained, finely chopped

• 1 anchovy fillet, finely chopped

• 1 eschalot, finely diced

• 1 tbsp flat-leaf parsley leaves, chopped

• 1 tsp French tarragon leaves, finely chopped

• 150g mayonnaise

• sea salt

• freshly ground white pepper

• lemon juice, to taste