Add the chicken broth, frozen corn, chopped potatoes, onion, garlic, salt and pepper into the insert of the Instant Pot. Stir together. Cover with lid and set the valve to the sealing position. Select manual setting and adjust pressure to high. Set the timer for 15 minutes.
When finished cooking, do a controlled quick release.
Select saute setting and set to low heat (if your IP does not let you select a heat setting, just select saute).
Mix half and half and cornstarch together and pour into the chowder.
Cook and stir for 3-5 minutes or until thickened
Add shredded cheese and stir to combine
Turn off IP and serve. Top with toppings, if desired.