Heat up your pressure cooker: press Saut, click on the Adjust button, select More to get the Saut More function, which means that the food will be sauted over medium-high heat. Wait for the Instant Pot indicator to read HOT.
Add sliced beef to a large ziplock bag, add 1 tablespoon cornstarch and shake well to coat the beef evenly.
Add the oil to the hot Instant Pot, once the oil is hot, add the beef and saut for 2-3 minutes, stirring a few times. If needed brown the beef in batches, you don't want to add too much as it will start releasing juice and it won't brown well. Note: You can also skip browning the beef and just add it to the pot!
If bits of beef stuck to the pot, add 1/2 cup water and deglaze the pot. Using a wooden spoon scrape the bottom of the pot. You can discard that liquid if wanted.
Add the rest of the ingredients to the pot: minced garlic, minced ginger, lite soy sauce, brown sugar, water, rice vinegar, and red pepper flakes. You can add less sugar, based on your taste and preference. Note: You can also skip browning the beef and just add it to the pot!
Stir well until all the ingredients are combined and coated in sauce.
Close lid and pressure cook at High Pressure for 8 minutes + 10 minutes Natural Release. Turn off the heat. Release the remaining pressure after the 10 mins No time has passed.. Open the lid.
Make the cornstarch slurry, in a small bowl mix cornstarch with water until fully combined. With the Instant Pot on the Saut function, add the slurry to the pot, stir to combine and cook for 2-3 minutes on Saut, stirring occasionally, until the sauce thickens. Turn off the Instant Pot and let the Mongolian Beef sit for 8-10 minutes before serving, in this time the sauce will settle and thicken more.
Serve over rice and garnish with fresh chopped green onions and sesame seeds.
