Season fillets with salt to taste. Brush meat side with egg white. Spread sesame seeds on plate and gently press each fillet, meat-side down, into sesame seeds to coat. Melt butter in large non-stick skillet over low heat. Place fillets sesame-side down in pan and cook about 3 minutes, or until slightly golden on bottom. Turn over each halibut fillet, cover and cook over low heat until fish flakes easily when tested with a fork (4 - 5 minutes; cooking time will vary depending on thickness of halibut).