Combine all liquid ingredients in a bowl. Whisk and set aside.
Turn Instant Pot on to sauté and add a Tablespoon or two of sesame oil. When hot, add the onion and cook for three or four minutes, stirring often. Add the garlic and stir for about a minute.
Add the chicken and sear both sides until chicken is no longer pink.
Pour the sauce over the chicken, deglazing the pot so no browned areas are left on the bottom of the pan.
Set manual/pressure cook for 10 minutes. Allow for a 10 minute pressure release. Release the rest of the pressure and put pot back on sauté.
Make a slurry of the cornstarch and water, add to the sauce and stir. Cook for 5 minutes, stirring often, to thicken the sauce. In the meantime, microwave the broccoli or add to the IP to cook with the rest of the ingredients.