In a shallow bowl, mix together 1/2 cup of sesame seeds, seasoning salt, white pepper, onion powder, wasabi powder, salt and flour; set aside. In a separate bowl, mix together the eggs and milk.
Dip tuna steaks in the egg mixture, then coat with the flour mixture until well coated on both sides. Press on as many extra sesame seeds as possible, so it is well coated. Heat the vegetable oil in a large heavy frypan over medium-high heat. Fry tuna steaks for 2 minutes per side, and immediately remove from heat. The inside of the fish should still be red.
To make the soy miso dressing, mix together the miso soup mix and soy sauce. Heat in a small saucepan or microwave, and drizzle over steaks.