In a medium bowl, add the meat, cornstarch, 1 tablespoon soy sauce, and 1 tablespoon oil and use your hands to toss to coat.
In a small bowl, mix together the remaining ¼ cup soy sauce, rice vinegar, water, sesame oil, sweetener, and ginger (if using).
In a large skillet over high heat, warm 2 tablespoons oil. Once the pan is very hot and oil is shimmering, add the veggies, white/light green scallions (if using), and a pinch of salt (you should hear a lot of sizzling). Stir everything together, then let it cook for 2-3 minutes, stirring occasionally, or until the veggies have softened (they’ll cook more later). Transfer to a bowl or plate.
Add the remaining 1 tablespoon oil to the hot skillet and swirl to coat. Add the meat, spread out evenly, and let it cook, undisturbed, for 3 minutes or until almost all the way cooked through and nicely browned. Add the veggies back in and give the meat a stir with a spatula to release it from the pan and mix everything together. Pour in the sauce, give it a stir, and let it simmer for about 2 minutes or until the sauce thickens.
Serve over your starch of choice. Top with the green scallions (if using), sesame seeds, and avocado (if using).