How to Make It
Melt 2 tablespoons of the butter in a large skillet over medium heat. Add the onion, ½ teaspoon salt, and ¼ teaspoon pepper and cook, stirring occasionally, until softened, 6 to 8 minutes.
Add the rice and cook, stirring, for 2 minutes. Add the wine and simmer until absorbed.
Add half the broth (1 ¾ cups) and simmer, stirring once, until absorbed, 8 to 10 minutes. Add the remaining broth and simmer, stirring once, until the rice is tender and creamy, 8 to 10 minutes. (If the rice is not cooked through and the mixture is dry, add more broth and continue to cook until tender.)
Stir in peas and scallions and cook until heated through, 2 to 3 minutes. Stir in the Parmesan and the remaining tablespoon of butter. Sprinkle with the parsley and additional Parmesan, if desired.