Stir together sherry, soy sauce, garlic, sesame oil, red pepper flakes in 1 cup glass measuring cup.
Transfer 1/2 of mixture to a large Ziploc bag and add beef. Seal bag and turn to coat beef. Refrigerate up to 2 hours to marinate.
Add cornstarch and equal parts cold water to make a slurry. Stir until smooth. Depending on how much thickening your sauce needs...you can make a larger amount of slurry by combining equal amounts of cornstarch and cold water.
Put 1 tablespoon of Oil in the instant pot on saute mode.
Dump the marinated beef and sauce from the ziploc bag into the pot and sear it, till it no longer pink.
Add rest of the sauce and beef broth and pressure cook on HIGH for 5 minutes.
Once the IP beeps, release the steam using the "quick release" process.
Turn it back on the saute mode and add the broccoli.
Let it simmer in the sauce for 5 minutes till the broccoli is cooked, but still crunchy.
Add the cornstarch slurry and let til simmer for another minute, till the sauce becomes thick and it coats the meat and the veggies.
Server hot with Brown rice or with Weight Watchers Cauliflower Fried Rice.