Combine the 2 tbsp white wine vinegar, 10 fluid ounces white wine and 1/4 cup minced shallots in a small saucepan over medium heat. Simmer until the liquid is reduced to about 2 tbsp. Strain out shallot and discard, return liquid to the pan. Stir 1 tbsp wasabi paste, or to taste and 1 tbsp soy sauce into the reduction in the pan. Over low heat, gradually whisk in 1 c. butter cubed - one cube at a time - allowing the mixture to emulsify. Be careful not to let the mixture boil. When all of the butter has been incorporated, stir in 1 c. chopped cilantro, and remove from heat. Pour into a small bowl, and set aside. Heat a large skillet over medium-high heat. Brush tuna steaks with olive oil, and season with salt and pepper. Place in the hot skillet, and sear for 3 to 5 minutes on each side. Be careful not to overcook, this fish should be served still a little pink in the center. Serve with sauce.