Start by patting the beef cubes dry with paper towels and seasoning them generously with salt and pepper on all sides.
Set your Instant Pot to the Sauté mode. Once hot, add the sesame oil, allowing it to warm for about a minute.
Working in batches, add the beef cubes to the pot. Brown each batch for approximately 3-4 minutes on all sides until they develop a nice crust. Once browned, remove the beef and set it aside on a plate.
In the same pot, add the minced garlic and grated ginger. Sauté for about 30 seconds, stirring constantly, until fragrant.
Carefully pour in the soy sauce, brown sugar, rice vinegar, and beef broth. Stir everything together until the sugar is dissolved and well mixed.
Place the browned beef back into the Instant Pot, ensuring the pieces are well submerged in the sauce.
Close the lid securely on the Instant Pot and set it to Manual mode. Adjust the time to cook for 35 minutes.
Once the cooking cycle completes, allow for a natural pressure release for about 10 minutes. Then, switch the vent to quick release to release any remaining steam.
In a small bowl, whisk together the cornstarch and cold water to create a slurry. Stir this mixture into the sauce in the pot; then, switch the Instant Pot back to Sauté mode. Cook for an additional 3-5 minutes, stirring frequently, until the sauce thickens to your desired consistency.
Dish out the teriyaki beef while hot, serving it over fluffy cooked rice or noodles. Finish with a sprinkle of sliced green onions and sesame seeds.
Notes
For an elegant look, serve in deep bowls with a well in the center of the rice for the beef.