I like my ahi cooked. I know there are some individuals out there who think this a travesty. But honestly, I have trouble eating raw meat or fish. At a restaurant recently I ordered a seared duck breast and got just that - seared on the outer nano-inch and raw in the middle. Yuk! Sorry, I can do medium rare and sometimes rare, but not raw. So as you can hopefully see in the photo to the left, the ahi is a bit more than lightly seared - the mainstream method. Rather, it's cooked quite a bit with just some red, raw flesh in the middle. You all can do what you want but this is how I like it. The wasabi-garlic marinade is adapted from a recipe on the Epicurious web site and comes from Bon Appetit Magazine. Enjoy!
Combine the soy, wasabi and garlic powder. Pour into a glass dish large enough to hold tuna steaks. Turn steaks over several times to coat. Let stand for 15-20 minutes, but no longer than 1/2 hour. (Barring the use of garlic powder, you could take a peeled garlic clove, smash it, then using the side of a chef's knife blade, mash it with a pinch of Kosher salt until it becomes a paste - a very gourmet thing to do.)
Cook beans by steaming, boiling or microwaving, just until tender-crisp. Drain and set aside.
In a skillet over med-high heat, heat oil to shimmering. Sprinkle tuna with toasted sesame seeds and place in pan, reserving the marinade. Sear tuna 3 minutes per side for medium rare - the steaks will be rare just in the middle. Place steaks on plates and tent with foil to keep warm. Add the marinade and green beans to the skillet and toss with tongs, coating the beans until they are heated through and sauce is reduced and slightly thickened.
Place beans beside tuna on plates and pour remaining sauce over both.
The white stuff on the plate above the Ahi is steamed cauliflower mashed with fat-free half & half. It's a healthful alternative to mashed potatoes.