In a medium bowl, whisk together soy sauce, water, and cornstarch until the cornstarch is completely dissolved. Whisk in remaining sauce ingredients until smooth. Set aside.
Heat oil in a large non-stick skillet over medium-high heat. Add chicken; cook and stir for about 5-6 minutes, or until browned and no longer pink inside.
Remove chicken from skillet and set aside.
Pour sauce into the skillet and bring to a gentle boil, whisking the entire time. Reduce heat to low, and simmer until thickens. Keep your eye on it and whisk regularly so that it doesn’t burn (this only takes 2-4 minutes).
Meanwhile, microwave broccoli according to package instructions.
When sauce reaches desired thickness, add cooked chicken back to the skillet, along with the drained pineapple chunks and the cooked broccoli. Stir until warmed through and coated in sauce.
Serve over rice, if desired.