Prep the Chicken: In a bowl, toss chicken cubes with 1 tablespoon cornstarch. Set aside.

Make the Sauce: In a small bowl, whisk together water, soy sauce, rice vinegar, sesame oil, brown sugar, and remaining 1 tablespoon cornstarch.

Sauté Garlic: Heat 1 tablespoon olive oil in a large skillet over medium heat. Add minced garlic and red pepper flakes. Cook for 3-5 minutes, or until garlic is golden brown.

Simmer Sauce: Pour the sauce into the skillet with the garlic. Bring to a simmer and cook for 5-7 minutes, or until the sauce has thickened slightly. Remove the sauce from the skillet and set aside.

Cook Chicken: Heat remaining 1 tablespoon olive oil in the same skillet over medium-high heat. Add the coated chicken and cook until browned and cooked through, about 5-7 minutes.

Add Broccoli: Add broccoli florets to the skillet with the chicken and cook for 2-3 minutes, or until tender-crisp.

Combine and Serve: Pour the reserved sauce over the chicken and broccoli. Cook for 3-4 minutes over low heat, stirring occasionally, to warm the sauce through. Serve immediately over rice.