Bring a small saucepan of water to a boil. Add the broccoli and cook until bright green and knife-tender, 5 to 6 minutes. Drain and place in a bowl of ice water until chilled, then drain and set aside.

Whisk together the hoisin, oyster sauce, soy sauce, cornstarch, and sugar. Set aside half of the marinade for later.

Remove the flank steak from the freezer and slice lengthwise into three even strips. Slice each strip into 1/4-inch slices. Place the slices in a bowl with the baking powder and half of the marinade. Mix thoroughly, then let chill in the fridge for at least 30 to 45 minutes or up to 1 day.

Heat a large nonstick skillet or wok over medium-high heat. Add 1 1/2 tablespoons of vegetable oil. Place about half the beef into the skillet and let sauté without moving it until caramelized on one side, about 3 to 4 minutes. Toss and sauté until slightly pink, another 1 to 2 minutes. Scoop out and transfer it onto a sheet pan. Wipe out the skillet and repeat the process with the remaining beef.

Whisk together the remaining half of the marinade with the chicken stock.

In the now empty skillet, heat the remaining tablespoon of vegetable oil and add the scallion whites; sauté for 2 to 3 minutes. Then add the ginger and garlic, followed by the drained broccoli, Fresno chiles, and the second half of the marinade. Toss everything together, then cover and let simmer for about a minute.

Add the beef with any accumulated juices and the scallion greens. Remove from heat and toss until combined.