01 - Heat olive oil in a large heavy saucepan or Dutch oven over medium heat. Season diced chicken with salt and pepper, add to the pan, and cook until browned and cooked through, approximately 5 to 6 minutes. Transfer chicken to a plate and set aside.
02 - Add 1 tablespoon butter to the same pan. Sauté chopped onion until translucent and fragrant, about 3 minutes. Add minced garlic and stir continuously for 1 minute until aromatic.
03 - Add Arborio rice to the pan and cook, stirring constantly, for 2 minutes until the grains are lightly toasted and the edges become translucent.
04 - Pour in the white wine while stirring continuously. Continue stirring until the wine is completely absorbed by the rice, approximately 1 to 2 minutes.
05 - Add warm chicken stock one ladleful at a time (approximately 1/2 cup per addition). Stir frequently and allow each addition to be absorbed completely before adding the next ladleful. Continue this process for about 15 minutes.
06 - Stir in asparagus pieces and continue adding the remaining stock ladle by ladle. Cook for an additional 10 minutes until the rice is creamy and al dente (tender but with a slight bite at the center) and the asparagus is just tender-crisp.
07 - Return the cooked chicken to the pan. Stir in the remaining 2 tablespoons butter, Parmesan cheese, and lemon zest until the butter melts and the mixture becomes creamy. Taste and adjust seasoning with additional salt and pepper as needed.
08 - Remove from heat, cover the pan, and let the risotto rest for 2 minutes to allow flavors to meld. Garnish with chopped parsley and additional Parmesan cheese if desired. Serve immediately while hot and creamy.