1) Heat oil in large wok to fry tofu. When oil is hot, add tofu to wok. Stir around occasionally for even browning. Once tofu is beginning to turn golden, sprinkle in cornstarch, and stir (this will give the tofu a crispier/chewier texture).
2) While the tofu is cooking, you can par-cook your green beans. I did this in the microwave, with a bit of water for 5 minutes. You can steam, or boil them as well.
3) While tofu is browning, mix soy sauce, tahini, sriracha, hoisin, and sesame oil in bowl. Add green beans to wok once they are vibrantly green, and still a bit crunchy. During last 30 seconds to 1 minute of tofu and bean cooking time, stir in ginger and garlic.
4) Once tofu is golden and crispy, garlic and ginger are fragrant, and beans are done to your liking (this was only about a minute after everything was added to the wok, for me) turn off heat, and take wok off burner. Stir in sauce. Tahini should thicken the sauce, and you should have an even coating on everything. You can always adjust with more soy sauce, or tahini.
Source of recipe: A take on the szechuan green bean recipe.