Preheat the oven at 200`c. Clean the fresh fish from the inside, but leave the scales on. In a mixing bowl add the sea salt and table salt and lightly beaten egg whites. Mix thoroughly. Place the fish on the dish with the silicone paper underneath it. Cover the fish with the salt mixture – use your hands to do the salt on the fish. Bake the fish in the oven for 20 minutes, until the crust is golden brown. Once out of the oven, crack and remove the salt crust, fillet the fish and serve.