Bring stock to a simmer in a large saucepan. Keep warm over low heat, but do not boil.
Heat a Dutch oven over medium heat. Add oil to the pot; swirl to coat. (Everything from here on will be added to this pot.)
Add onion; cook 5 minutes, stirring occasionally.
Add the Arborio rice and salt, cook 1 minute, stirring frequently.
Add 1/2 cup stock; cook 2 minutes or until liquid is absorbed, stirring frequently.
Stir in 1 1/2 cups stock; cook 4 minutes or until liquid is nearly absorbed, stirring constantly.
Add remaining stock, 3/4 cup at a time, stirring nearly constantly until each portion is absorbed before adding the next (about 20-25 minutes); reserve 1/3 cup stock at last addition.
Remove pot from heat.
Stir in reserved remaining stock, butter, pepper, and cheese.
Top the risotto with parsley.
Be mindful of salt as the stock will likely already be salty enough. I felt the recipe needed an extra 1/4 tsp but use your own discretion. I also added a splash of cream at the very end just before serving, but this is optional.As a general rule: 1 cup of dry Arborio rice yields 3 cups of cooked rice.