01 - Toss the sliced flank steak with 1 tablespoon cornstarch until evenly coated, ensuring each piece is lightly dusted for tender results.
02 - Whisk together soy sauce, beef broth, brown sugar, sesame oil, minced garlic, fresh ginger, rice vinegar, and red pepper flakes in a medium bowl until sugar dissolves completely.
03 - Add the coated beef to the Instant Pot, pour the sauce mixture over, and stir to coat evenly. Seal the lid, set valve to Sealing, and cook on high pressure for 10 minutes.
04 - Quick release the pressure, open the lid, and add broccoli florets. Reseal the lid and cook on high pressure for 1 additional minute. Quick release again.
05 - Mix 2 tablespoons cornstarch with 2 tablespoons cold water to create a smooth slurry. Stir into the pot, switch to Sauté mode, and cook for 2-3 minutes until sauce thickens and broccoli reaches tender-crisp texture.
06 - Transfer to a serving dish and garnish with sesame seeds and sliced green onions. Serve immediately over steamed rice or noodles.