Cut tofu into ⅓ inch thick triangular slices, place in a large casserole dish, and set aside.
To create the marinade, thoroughly mix together the rest of the ingredients (except the oil) in a medium bowl and pour over the tofu. Allow tofu to sit for a minimum of two hours, or overnight for a richer taste. Flip tofu halfway in-between.
Once the tofu is marinated, place a large sauté pan over high heat. Add just enough oil to coat the bottom of the pan. Add as many tofu slices as will fit in one layer. Cook until tofu is browned on the bottom, 2-3 minutes. Flip the pieces, and brown on the other side, about 2 minutes. Pour in the marinade mixture, and cook until tofu darkens slightly, about 45 seconds. Flip tofu and repeat.
Garnish with remaining thinly sliced green onion.