Heat the butter and oil in a large skillet or saucepan over medium heat. Add the onion and sauté until translucent, 3 to 4 minutes.
Add the rice and stir until coated. Add the wine and stir until all the liquid is absorbed. Add 1 cup of the broth and cook until absorbed, stirring occasionally.
Add the remaining broth ½ cup at a time, waiting until each portion is absorbed before adding the next. Continue until the rice is cooked al dente, about 35 minutes. Stir in the Parmesan, 1 teaspoon salt, and ¼ teaspoon pepper.
Meanwhile, puree 2 cups of peas in a blender or food processor.
Before serving, stir the peas into the rice until fully incorporated, then fold in remaining whole peas. Garnish with the mint, if desired.
Tasty. Will make again.