Preheat the grill to high and lightly oil a baking tray.
Boil the new potatoes in a pan of water for 10-12 minutes until soft.
Score the back of the fish fillets gently to prevent curling.
Coat the fish in seasoned flour, then clarified butter, and finally panko breadcrumbs.
Place the fish on the tray, drizzle with clarified butter, and grill for 5 minutes.
Drain the potatoes and toss with diced butter, salt, pepper, and chopped parsley.
Whisk egg yolks, salt, vinegar, and mustard powder until fluffy.
Steady drizzle in the sunflower oil while whisking constantly and divide into two bowls.
Mix onion, cornichons, anchovy, herbs, capers, cayenne, and lemon juice into one bowl for remoulade.
Mix chopped capers, gherkins, shallot, dill, parsley, and lemon juice into the second bowl for tartare sauce.
Serve fish with potatoes, lemon wedges, and the two sauces.