Combine water or broth, soy sauce, honey, garlic and pepper in Instant Pot. Whisk until honey dissolves.
Add the chicken breasts to the Instant Pot.
Seal the lid and move the steam valve to the sealing position.
Set Instant Pot to pressure cook/manual, high pressure. Set the cook time according to the size of your chicken breasts. For fresh (not frozen) chicken: 8 minutes for small (7-8 ounce) chicken breasts, 10 minutes for medium (10 ounce) chicken breasts, or 11 minutes for large (12 ounce) chicken breasts. For frozen chicken breasts, add 3 minutes to the cooking times listed in step 4, and pressure cook (manual) at high pressure. Be sure that your chicken breasts are not stuck together as that will increase the pressure cook time.
The Instant Pot will take about 10 minutes to come to pressure and then will start counting down the cook time. When the cook time ends, carefully quick release the pressure by using the handle of a long spoon to move the steam valve to venting. (If your chicken breasts were frozen, do a 10 minute natural release instead of a quick release. Just leave the Instant Pot alone for 10 minutes before moving the steam valve to the venting position.) Wait for the steam to escape and the pin to drop down. Then, carefully remove the lid.
Use an instant read thermometer to test the internal temperature of the chicken. It should be at least 165° F. If the temperature is lower, finish cooking the chicken using the Instant Pot's sauté function.
Remove chicken to a clean plate or cutting board.
In a small bowl, stir together the 2 teaspoons cornstarch and 1 tablespoon water. Turn the Instant Pot on saute mode and stir in the cornstarch mixture. Cook, stirring, until the liquid has thickened, 2-3 minutes. Turn off Instant Pot and remove the inner pot to stop the cooking process.
Slice the chicken and serve it with the honey garlic sauce, plus rice and vegetables, or as desired.