Rub tuna steaks with about 1 tsp. sesame oil, and salt and pepper both sides.
Put a large pot of water and 2 tsp. salt on high heat for pasta.
To a medium saute pan, add 1 tsp. sesame oil and 1 tsp. canola oil over medium-high heat. Add garlic and ginger. Saute until fragrant and golden, but not brown.
Add sliced shiitake. Stir occasionally, cooking until edges begin to caramelize.
While shiitake cook, cook the soba noodles according to package instructions (mine take 7-8 minutes, but this varies). Fresh soba take only 1-2 minutes so be careful. Drain. Drizzle with a scant 1 tsp. sesame oil and a sprinkling of tamari or soy sauce. Toss thoroughly, and set aside.
Get a stove top grill pan or outdoor grill very hot (you want to sear the fish). We usually go for medium rare with this, but cook it the way you like it. My tuna steaks usually get about 2 minutes on each side, and they're pretty thick. Remove from the pan, and slice.
Add wine to the saute pan with the mushrooms. Reduce until most of the wine is cooked off.
Add the half n' half. Whisk the sauce to combine. Turn off the burner.