Marinate the Beef

Slice the steak thinly against the grain (about ¼ inch thick).

In a bowl, combine soy sauce, oil, cornstarch, baking soda, salt, and pepper.

Mix by hand until evenly coated. Let marinate for 10–15 minutes while you prepare the sauce and vegetables.

Make the Sauce

Whisk together broth, soy sauces, sugar, and cornstarch in a bowl until smooth.

Set aside.

Steam the Broccoli

Add ¼ cup water to a large skillet or wok and bring to a simmer over medium-high heat.

Add the broccoli florets, cover, and steam for 1–2 minutes, until bright green and slightly tender.

Remove from the pan and set aside. Wipe away any remaining water.

Cook the Mushrooms

Add ½ tablespoon oil to the same pan.

Add the mushrooms and sauté for 3–4 minutes, stirring occasionally, until golden brown and lightly caramelized.

Transfer to a bowl and set aside.

Sear the Beef

Increase heat to high and add the remaining ½ tablespoon oil.

Spread the marinated beef in a single layer and cook without stirring for about 30 seconds until browned on one side.

Flip and cook another 30–45 seconds, or until just cooked through.

Add Aromatics and Combine

Lower the heat to medium-high.

Add the garlic and ginger; stir quickly for 20–30 seconds, releasing their fragrance.

Return the broccoli and mushrooms to the pan.

Give the sauce another quick stir (to dissolve any settled cornstarch), then pour it into the pan.

Cook and toss everything together for 1–2 minutes, until the sauce thickens and coats the ingredients evenly.

Serve

Transfer to a serving dish and enjoy immediately with steamed rice or noodles.

Garnish with sesame seeds or sliced scallions if desired.