In a medium bowl, whisk together all the ingredients to make the Instant Pot Beef and Broccoli Sauce and set it aside.
Select the sauté mode on your Instant Pot and wait for it to read HOT.
Next, add oil to the Instant Pot insert. Once the oil is heated, place the beef strips in the bottom of the insert a single layer. (You will have to cook in batches).
Let the beef sear for 2 minutes and then turn it over to sear the other side for 2 minutes or until the beef is golden brown. Remove and set aside on a plate.
Add ¼ cup water to the Instant Pot insert, and use your wooden spoon to deglaze the pot.
Place the beef back in the Instant Pot, then add in the sauce mixture and stir to combine it all.
Close the lid, set the valve to the sealing position and set to manual pressure/high pressure for 10 minutes.
When done, allow for a 10-minute natural pressure release, then perform a quick pressure release. Remove the beef and set aside on a plate.
In a small bowl, mix together cornstarch and water until combined and there are no lumps.
Press sauté on your Instant Pot, add the slurry to the pot and stir to combine. Cook the slurry for about 2-3 minutes, or until the sauce has thickened.
Stir in the broccoli and cook for about 1-2 minutes. Turn off the Instant Pot, add the beef back in and store to combine.
Top your Instant Pot Beef and Broccoli with sliced green onions, sesame seeds, and serve.