In a large glass measuring cup, whisk together all the ingredients for the sauce, up to the ground white pepper. Make a slurry by mixing the tapioca starch and water together, and then measure out your sesame seeds. Next, cut the chicken into bite size pieces. If you are planning on serving this dish with a side of rice, now would be a good time to cook the rice, too!
Now that your mise-en-place is completed, pour 1 or 2 tablespoons of healthy cooking oil in a large, skillet set over high heat. When the pan is hot enough, add about half the pieces of chicken and let the meat cook undisturbed for about 2 minutes, until the chicken turns opaque about half way up and gets nice and golden at the bottom. Flip the pieces of chicken and continue cooking for another minute or two, until browned on the other side. Remove to a plate and repeat with the remaining chicken.
Once all the meat is cooked, return it to the skillet and add sauce. Lower the heat and simmer, uncovered, for about 5 minutes, to finish cooking the chicken. Give your slurry a good stir and then whisk it into the simmering sauce. Stir constantly for about a minute, until the sauce is thickened, then add the toasted sesame seeds and stir until well incorporated.
Serve immediately with a side of rice and garnished with a little bit of chopped green onions, if desired.