Prep the beef: Slice the flank steak thinly against the grain.
Sauté the beef: Turn your Instant Pot to “Sauté” mode. Add the olive oil. Brown the beef in batches for 1–2 minutes per side. Remove and set aside.
Make the sauce: In a bowl, whisk together soy sauce, honey, minced garlic, and sesame oil.
Pressure cook: Return all the beef to the pot and pour the sauce over it. Seal the lid, set to “Manual” or “Pressure Cook” on high for 10 minutes. Let pressure naturally release for 5 minutes, then quick release the rest.
Steam the broccoli: While the beef cooks, steam the broccoli until just tender (about 2–3 minutes in the microwave or on stovetop).
Thicken the sauce: Switch the Instant Pot back to “Sauté.” Stir together cornstarch and water to make a slurry. Pour it into the sauce and stir until thickened (1–2 minutes).
Combine: Add the steamed broccoli and toss to coat in the sauce.
Serve: Spoon over steamed rice or noodles and top with optional garnishes.