Whisk together broth, Splenda (or sugar), soy sauce, vinegar and ginger. Set aside. Wait until just before pouring over the meal to add in the cornstarch. (Otherwise it gets gloopy and slugdy.).
Spray a wok or non-stick skillet liberally with Pam (or drizzle in some vegetable oil to coat the bottom). Add scallions, garlic and red pepper flakes. Cook for 2-3 minutes.
Add chicken and brown. Use more spray (or oil) if necessary to assist with the browning. Cook about 5-8 minutes. The chicken should be almost done before you add the sauce.
Add cornstarch to your sauce bowl (put together in step one) and whisk to create a slurry. Add to your chicken in the pan and heat until boiling, then reduce to a simmer. The boiling of the sauce will cause the cornstarch to thicken. Soon it will be as thick as the General Tso's sauce you're used to!