01 - Heat olive oil in a large, heavy-bottomed saucepan or Dutch oven over medium heat. Season diced chicken generously with salt and pepper. Add to the hot pan and cook, stirring occasionally, until golden brown and cooked through, approximately 5-6 minutes. Transfer chicken to a plate and reserve.
02 - Reduce heat to medium-low. Add 1 tablespoon butter to the same pan. When melted, add diced onion and cook, stirring frequently, until translucent and softened, about 3 minutes. Add minced garlic and cook for 1 additional minute until fragrant.
03 - Increase heat to medium. Add Arborio rice to the pan and cook, stirring constantly, for 2 minutes until rice grains are translucent around the edges and lightly toasted.
04 - Pour in white wine and stir continuously until completely absorbed by the rice, approximately 1-2 minutes.
05 - Add warm chicken stock one ladleful at a time (approximately ½ cup per addition), stirring frequently. Wait until each addition is nearly absorbed before adding the next. Continue this process for 15 minutes.
06 - Stir in asparagus pieces. Continue adding remaining stock ladle by ladle, stirring frequently, for an additional 10 minutes. The risotto is ready when rice is creamy but al dente with a slight bite in the center and asparagus is tender-crisp.
07 - Return cooked chicken to the pan. Remove from heat. Stir in remaining butter, grated Parmesan, and lemon zest until butter melts and cheese is incorporated. Taste and adjust seasoning with salt and pepper as needed.
08 - Cover pan and let risotto rest for 2 minutes to allow flavors to meld. Transfer to serving bowls, garnish with chopped parsley and additional Parmesan if desired. Serve immediately while hot and creamy.