Bring the vegetable or chicken broth to a gentle simmer in a pot and keep it warm.

In a large pot or Dutch oven, heat the olive oil over medium heat. Add the finely chopped onion and sauté until translucent, about 5 minutes.

Add the Arborio rice and stir to coat with oil. Toast the rice for 1-2 minutes.

Add a ladle of warm broth to the rice and stir until absorbed. Continue adding broth one ladle at a time, stirring frequently, until the rice is al dente, about 18-20 minutes total.

Stir in the peas when the rice is halfway cooked, about 10 minutes into cooking.

Remove the pot from heat and stir in the unsalted butter and grated Parmesan cheese until melted and creamy.

Season with salt and pepper to taste. Garnish with fresh parsley and serve immediately.