Rinse and pat dry the flank steak.
Press SAUTE function on the Instant Pot and wait until it's HOT. Add in 1 tablespoon vegetable oil.
Add the flank steak and sear until browned, about 3-4 minutes per side.
Push the steak aside and add in the remaining 1 tablespoon of oil.
Add in the minced shallot and garlic and sauté until softened and fragrant, about 2-3 minutes.
Add in the grated Asian pear.
In a bowl, combine together soy sauce, brown sugar, 1 teaspoon sesame oil, ground ginger, ground coriander, and red pepper flakes (optional). Give it a stir.
Pour the sauce over the flank steak and coat evenly.
Cover with the lid and set to SEALING.
Press the MEAT/STEW function and cook for 40 minutes at HIGH PRESSURE, with natural release.
Transfer the meat to a bowl and shred with a fork.
To concentrate the liquid/"jus," leave it in the pot and press the SAUTE function. Let the liquid evaporate and thicken a little.
Pour the liquid over the meat and garnish with remaining 1 teaspoon sesame oil and chopped green onions.
Serve the shredded Korean bulgogi beef with warmed tortillas and your choice of toppings.