Step 1

Pat meat dry, then toss with 3 teaspoons cornstarch. Stir together broth, ginger, black-bean sauce, sugar, sesame oil, and remaining 1 teaspoon cornstarch in a bowl. Measure 2 tablespoons water in a separate small bowl and set aside.

Step 2

Heat a large, heavy skillet (preferably cast iron) or wok over high for 3 minutes. Swirl in 2 tablespoons vegetable oil. Working in batches to avoid crowding pan, brown meat, about 1 minute per side. Transfer to a plate.

Step 3

Swirl in remaining vegetable oil and add broccoli. Cook, stirring occasionally, until broccoli begins to brown, about 3 minutes. Add reserved water and toss until broccoli is bright green and tender, 1 to 2 minutes more.

Step 4

Add white and light-green parts of scallion to skillet along with meat and any accumulated juices. Stir in black-bean-sauce mixture and toss until evenly coated and sauce has thickened, about 30 seconds. Serve with rice, sprinkled with scallion greens.