In the cooker, heat 2 TBLS of butter over medium heat. Saute 1 small onion - finely chopped - for 4-5 minutes, until soft. Stir frequently so the onion does not brown. Add the 1 cup of Arborio rice (or other short grained rice) and saute until light brown. Add 1 cup of frozen peas and 2 1/4 cup of chicken broth; stir well. Close the lid and bring to pressure. Lower the heat and cook for 7 to 13 minutes. (some cookers have two positions the times are for Position 1 and 2 respectively)
Release the pressure and open the lid. Stir in an additional 1 TBLS of butter, 1/3 cup of Parmesan cheese and 1/8 tsp of black pepper. Let sit until butter and cheese melts then stir thoroughly.