Heat the olive oil in the wide pan over medium heat until shimmering and fragrant. Add the finely chopped onion and cook, stirring occasionally, until translucent and soft—about 3-4 minutes, with a gentle sizzle and sweet aroma filling the air.
Add the Arborio rice to the pan. Stir constantly, toasting the rice lightly until its edges turn slightly translucent and it starts to smell nutty—about 2-3 minutes. You'll notice a gentle crackling as the rice toasts.
If using, pour in the white wine. Stir until the wine is mostly absorbed, about 1-2 minutes, and the rice begins to look glossy and plump.
Start adding the warm vegetable broth, about half a cup at a time. Stir constantly, allowing each addition to be absorbed before adding the next. This slow process, with gentle bubbling, will take about 20 minutes, during which the rice gradually becomes tender and creamy.
When the rice is just tender but still has a slight bite (al dente), gently fold in the thawed or blanched green peas. Continue stirring for another 2 minutes, letting the peas release their bright juices and color.
Remove the pan from heat. Stir in the grated Parmesan cheese and cold butter until melted and creamy—this adds richness and a silky finish. If using, sprinkle the lemon zest over the top for a fresh, citrusy brightness.
Allow the risotto to rest for 2 minutes, uncovered. This helps the flavors meld and the texture to set to a luscious, velvety consistency.
Give it a final gentle stir, then serve immediately, garnished with extra Parmesan or a drizzle of olive oil if desired. The dish should be vibrant green, creamy, and inviting with a slight jiggle on the plate.
