Prepare Instant Pot insert, cook grits: Liberally coat the insert of a 6-quart programmable pressure multicooker (such as Instant Pot) with cooking spray. (Times, instructions, and settings may vary according to cooker brand or model.) Add water, grits, and salt to cooker; stir gently to combine, allowing grits to fall in an even layer in bottom of insert. Cover cooker with lid, and lock in place. Turn steam release handle to SEALING position. Select MANUAL/PRESSURE COOK setting. Select HIGH pressure for 10 minutes. (It will take 9 to 10 minutes for cooker to come up to pressure before cooking begins.)
Release pressure: Let the pressure release naturally for 15 minutes. Carefully turn steam release handle to VENTING position, and let steam fully escape (float valve will drop). (This will take about 5 minutes.)
Add remaining ingredients: Remove lid from cooker. Add cheese, half-and-half, butter, parsley, and pepper to grits in cooker, stirring until cheese is melted and grits are creamy. Garnish with additional parsley and pepper; serve hot with additional butter.
