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