Preparation Bring stock to a simmer in a small saucepan. Cover and keep warm. Melt 2 tablespoons butter with 1 tablespoon oil in a large heavy pot over medium heat. Add onion and sauté until soft (do not brown), about 5 minutes. Add pancetta and cook until light brown, about 3 minutes. Add rice and cook, stirring until coated, about 1 minute. Add 1 cup stock. Stir constantly with a wooden spoon until stock is almost absorbed, about 1 minute. Continue adding stock by the cupful in 5 more additions, stirring constantly and allowing stock to be absorbed between additions, until rice is almost tender. Add peas and remaining cup of stock and cook, stirring constantly, until the rice is creamy and tender but still firm to the bite, about 22 minutes total. Stir in 1/4 cup hot water if rice seems dry. Remove pan from heat. Stir in the remaining 1 tablespoon butter, 1 tablespoon oil, Parmesan, and parsley. Season rice and peas with salt and pepper. Transfer to serving bowls or plates, and serve.