Blend sesame seeds, garlic powder, salt and peppers. Brush or mist fish with oil. Pack on a heavy layer of the seed mixture; turn and repeat, covering all surfaces with as much of the seed blend possible.
Preheat a heavy frying pan, wok or grill with medium high to high heat, drizzle or mist with oil and quickly sear fish to brown the outside leaving the inside from raw to medium rare. Remove and rest for at least five minutes. Separate the fish into two portions.
To Assemble: Cover the bottom of flat serving bowls with rice and top with seared seafood. Sprinkle minced cucumber over the top of the fish. Serve alongside steamed or stir fried veggies with small cut sheets of nori, soy sauce, wasabi and pickled ginger on the side.
To Make the Sushi Rice: Wash rice well, stirring with fingers until water runs clear; drain well. To a pot with a tight fitting lid, place water and rice in the pot. DO not cover the pot yet. Over high heat, bring to a simmer. Once the rice is simmering, cover rice and reduce the heat to medium low. Cook for 10 minutes without removing the pot lid at all. Turn heat down to the lowest setting and cook for another 10 minutes. Next, turn off the heat and let the rice sit in the pot on the stove for 15 minutes. (Note: Follow instructions carefully.) Transfer to large mixing bowl.
Combine rice vinegar, sugar and salt. Sprinkle vinegar mixture over rice and stir well with a wooden spoon using a slicing motion. Cover with a wet towel and reserve.