Combine the white vinegar, wine and shallots in a small saucepan over medium heat. Simmer until the liquid is reduced to about 2 tablespoons. Strain out shallot and discard, return liquid to the pan.
Stir the wasabi and soy sauce into the pan. Over low heat, gradually whisk in butter 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 the coriander and remove from heat. Pour into a small bowl, and set aside.
Heat a large frypan over medium-high heat. Brush tuna steaks with olive oil and season with salt and pepper.
Place steaks in the hot frypan 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 centre. Serve with sauce.