Turn Instant Pot to sauté. Add in butter and melt. Add onions, carrots, and celery and sauté for 5 minutes. Pour in the broth. Add chicken and seasonings.
Pour in veggies and half and half. Turn to sauté. Make a cornstarch slurry. Stir mixture in. Once thickened and cooked, turn off the pot. Salt and pepper to taste.