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