Press the tofu. Start out by pressing your tofu for 30 minutes. Press it in a tofu press, or if you don't have a tofu press, place the block of tofu on a plate with another plate on top of it and then stack a heavy pot on top. The goal is to remove any excess water from the tofu so it's as firm as possible.
Make the teriyaki sauce. While the tofu is pressing make your teriyaki sauce. Add soy sauce, 1 cup of water, rice vinegar, maple syrup, sesame oil, brown sugar, ground ginger and garlic powder to a saucepan and bring to a simmer, stirring all the while. Make up a cornstarch slurry by adding the cornstarch to a bowl with ¼ cup water and mixing it into a paste. Add this to your sauce and whisk it in. Keep stirring until the sauce thickens. Turn off the heat.
Fry the tofu. When the tofu is pressed, cut it into slices, cut the slices in half and then into triangles. Heat sesame oil in a frying pan and when hot, add the tofu triangles and fry until browned and crispy on one side, and then turn them over and fry until browned and crispy on the other side. Stand the tofu triangles on their sides and fry so that the sides get browned and crispy too.
Add the sauce. Pour the sauce into the pan and use a spatula to gently mix the tofu with the sauce so that it's evenly distributed. Turn off the heat.
Serve. Serve it over basmati rice topped with sesame seeds and chopped green onions with lemon wedges on the side.