01 - Toss the sliced beef with 1 tablespoon cornstarch until evenly coated.
02 - Whisk together soy sauce, beef broth, brown sugar, sesame oil, garlic, ginger, rice vinegar, and red pepper flakes in a medium bowl.
03 - Add the coated beef to the Instant Pot, then pour the sauce mixture over. Stir to combine thoroughly.
04 - Seal the Instant Pot lid and set the valve to Sealing. Cook on high pressure for 10 minutes.
05 - Quick release the pressure. Open the lid and add the broccoli florets.
06 - Reseal the lid and cook on high pressure for 1 additional minute. Quickly release the pressure again.
07 - Mix 2 tablespoons cornstarch with 2 tablespoons cold water in a small bowl to create a smooth slurry.
08 - Turn on Sauté mode and stir the slurry into the beef and broccoli mixture. Cook for 2-3 minutes until sauce thickens and broccoli is tender-crisp.
09 - Serve hot, garnished with sesame seeds and sliced green onions.