"When I bread tuna or swordfish," Rach says, "I never flour or egg the fish since it has enough moisture to attach to the crumbs naturally."
In a small bowl, whisk all the ingredients for the sauce.
For the green beans, in a large deep skillet, bring a few inches of water to boil. Prepare a large bowl of ice water. Salt the boiling water and add the green beans. Cook until crisp-tender, about 3 minutes. Drain the green beans and add to the ice water. Let cool, then drain well.
Heat a large cast-iron skillet over medium to medium-high.
In a shallow dish, mix the plain breadcrumbs, panko, sesame seeds, chili powder, granulated garlic, granulated onion, and ground ginger.
Season both sides of the tuna with salt. Coat the tuna with the breadcrumbs, pressing firmly so the crumbs adhere.
Add enough safflower oil to the bottom (about ¼ cup). When the oil begins to ripple, add the tuna. Cook until deep golden, about 3 minutes per side. Transfer to a wire rack.
Meanwhile, in a large nonstick skillet, heat the remaining 3 tablespoons safflower oil, three turns of the pan, over high. When the oil begins to smoke, add the green beans and scallions. Stir-fry until the green beans blister, about 3 minutes. Add the soy sauce, mirin, and sesame oil; season with salt and pepper.
Serve the crispy tuna on top of the sauce. Or top the tuna with the sauce. Garnish with chives. Serve with the green beans.