Stir in stock, cover and cook on high pressure for 5 to 6 minutes. 5 minutes will result in a slightly al dente risotto (similar to a stovetop risotto). 6 minutes will give you a super creamy risotto. Allow the pressure to release naturally. Stir in the Parmesan cheese and remaining 1 tablespoon butter, and continue to stir until the rice has absorbed the rest of the liquid and gets creamy (about 3 minutes). Season to taste with additional salt.