Halve the avocados, remove the stones, and peel away the skin.
Dice the avocado flesh into 1cm cubes and place in a large bowl.
Pour the juice of one lime over the avocados and toss gently.
Peel the mangoes and dice the flesh into pieces.
Combine the chili, onion, coriander, oil, and lime juice in a bowl and season with sea salt.
Stir the mango and avocado into the salad mixture.
Season the fish with salt and dust the filleted side lightly with flour.
Melt the butter in a frying pan and place fillets floured-side down.
Season the skin with pepper and fry gently for 5 minutes.
Turn the fish, remove the pan from heat, and rest for 3 minutes.
Plate the salad and serve the turbot drizzled with the remaining pan butter.