Cook the brown rice or quinoa according to the package instructions and set aside.
Thinly slice the flank steak against the grain and set it aside. Turn on the Instant Pot and press the "Saute" button. Allow it to heat up then add the steak and sear quickly on each side.
While the steak is searing, whisk together the coconut aminos or soy sauce with the minced garlic, minced ginger, and water.
When the steak is browned, cancel the saute feature on the Instant Pot and pour the liquid mixture over the browned steak. Lock on the lid and push the manual (or pressure cook) button on the Instant Pot and adjust the time to 11 minutes.
While the beef is cooking, whisk together the corn starch and 3 tablespoons of cold water
When the Instant Pot beeps, release the vent all at once, then carefully open the lid. Stir in the honey then stir in the corn starch and water mixture then add the chopped broccoli.
Push the "Saute" button again and heat the beef and sauce, stirring constantly until the sauce thickens and the broccoli is cooked, about 3-5 minutes.
Serve the Mongolian beef over brown rice and top with chopped scallions and sesame seeds.