Turn the Instant Pot on the Sauté setting and add the sesame oil. Add several of the chicken thighs, skin-side-down. Brown the skin for 2-3 minutes, until golden brown. Then remove the chicken thighs and repeat with the remaining thighs until all have been browned on the skin side. Place all the chicken thighs back in the Instant Pot, skin-side-up. *This first step is optional. Then skin will not stay crisp once pressure cooked, but the browning process gives the skin a much richer color once finished. If skipping the browning, pile the raw thighs in the Instant Pot and move onto step 2.
Pour the soy sauce, brown sugar, ketchup, garlic, and ginger in a bowl. Whisk well, then pour the glaze over the top of the chicken.
Lock the lid into place. Set the Instant Pot on Pressure Cook High for 20 minutes. Then turn the Instant Pot Off and perform a Quick Release . Once the pressure valve button drops, it's safe to open the lid.
Scoop 1/4 cup of the glaze out of the pot. Whisk 1 tablespoon cornstarch into the glaze. Then turn the Instant Pot back on Sauté and stir the cornstarch slurry back into the pot. Let it simmer for 2-4 minutes to thicken the glaze. Turn off the pot. Sprinkle with sesame seeds and chopped scallions before servings.
Don't have an Instant Pot? You can make this recipe in the slow cooker. Follow step 1 on the stovetop and place the chicken thighs in a slow cooker. Pour the glaze over the top. Then cover the slow cooker and set on high for approximately 6 hours. Follow step 4 to thicken the sauce.