Step One
Cut the flank steak into thin strips.
In a large bowl, toss the flank steak in the flour (working in batches if you need to) and set aside when done.
Step Two
In a medium bowl, combine the soy cause, rice vinegar, water, garlic, ginger, brown sugar, and red pepper flakes.
Step Three
Place the flank steak into the Instant pot and pour the soy sauce mixture over the meat. Stir it up until the meat is totally covered.
Note: many of the recipes I’ve tried call for browning the meat in sesame oil, in batches, before adding the sauce. I have attempted this step, found it sort of annoying, and decided to try and skip it. There is zero difference in the outcome of this dish – you do not need to brown the meat in this particular recipe.)
Step Four
Close the lid on your Instant Pot and set it to the Manual (high pressure) setting and set the timer to 15 minutes.
When the cooking time is over, allow the Instant Pot to natural release for 10 minutes and then use the quick release feature to depressurize the pressure cooker
Step Five
Serve this super yummy Mongolian Beef over rice and garnish with chopped green onions and sesame seeds!