In a small bowl, mix the black and white sesame seeds together. Set aside.
In another bowl, combine the soy sauce, olive oil, grated ginger, minced garlic, and a pinch of salt and pepper. Stir well.
Pat the tuna steaks dry with a paper towel, then brush both sides with the soy sauce mixture.
Carefully press each side of the tuna steaks into the sesame seed mixture, ensuring they are evenly coated.
Heat a non-stick skillet over medium-high heat. Once hot, add a drizzle of olive oil.
Sear the tuna steaks for about 1-2 minutes on each side for rare, or cook longer for desired doneness. For a firm exterior, be careful not to overcook.
Remove from heat and let rest for about 2 minutes before slicing the tuna into thin strips.
Arrange the mixed greens on a plate as a base. Top with avocado slices and arrange the sliced tuna over the top.
Garnish with wasabi and pickled ginger on the side for added flavor.
Notes
Plate the tuna artfully on a bed of greens, drizzle with any remaining soy sauce mixture from the pan, and sprinkle with extra sesame seeds for an elegant touch.