In a heavy saucepan or dutch oven, melt the butter over medium heat. Add the Arborio rice and sauté/toast the rice for 3 - 5 minutes until fragrant.
Add the diced onion and sauté until the onion is softened, about 5 minutes.
Add the white wine and stir until completely absorbed.
Begin adding the chicken broth, about 1/2 C at a time, stirring continuously until the liquid is absorbed.
When you get to the last of your chicken broth, add the remaining broth and your peas at the same time. Stir to combine, turn off the heat and cover. Let stand for about 10 minutes to steam the peas.
Add the grated Parmesan and lemon juice. Season generously with cracked pepper. Stir to combine and serve immediately.