Step 1

Make the sauce. Whisk the broth or water, soy sauce, hoisin, brown sugar, vinegar, sesame oil, 1 teaspoon of the cornstarch, ginger, and red pepper flakes together in a small bowl; set aside.

Step 2

Season and coat the chicken in cornstarch. Place the chicken in a medium bowl and season with the salt. Sprinkle the remaining 1/4 cup cornstarch over the chicken and toss with your hands until evenly coated, separating any pieces that are stuck together.

Step 3

Sear the chicken in 2 batches. Heat 2 tablespoons of the oil in a large nonstick or cast iron frying pan over medium-high heat until shimmering. Add half of the chicken and spread into an even layer. Cook undisturbed until golden brown on the bottom, 4 to 5 minutes. Flip and cook undisturbed until the chicken is browned on the second side and cooked through, 4 to 5 minutes more. Transfer to a plate. Add the remaining 1 tablespoon oil to the pan and repeat cooking the remaining chicken.Transfer to the plate.

Step 4

Cook the scallions. Add the scallions to the skillet and cook until fragrant and beginning to char, about 30 seconds.

Step 5

Add the sauce. Return the chicken and any accuulated juices to the pan. Rewhisk, then pour the sauce into the pan. Cook, tossing constantly, until the sauce thickens, is glossy, and coats the chicken, 30 seconds to 1 minute. Serve over rice, if desired.