01 - Heat olive oil in a large, heavy saucepan over medium heat. Add diced chicken, season with salt and pepper, and cook until browned and cooked through, about 5–6 minutes. Remove the chicken and set aside.
02 - In the same pan, add 1 tablespoon butter. Sauté the onion until translucent, about 3 minutes. Stir in garlic and cook for 1 minute more.
03 - Add Arborio rice and cook, stirring, for 2 minutes until the grains are lightly toasted.
04 - Pour in white wine, stirring until absorbed.
05 - Add hot chicken stock one ladleful at a time, stirring frequently and allowing each addition to be absorbed before adding the next. Continue for about 15 minutes.
06 - Stir in asparagus pieces and continue adding stock, cooking for another 10 minutes, until rice is creamy and al dente and asparagus is just tender.
07 - Return chicken to the pan. Stir in remaining butter, Parmesan cheese, and lemon zest. Adjust seasoning with salt and pepper.
08 - Remove from heat, cover, and let rest for 2 minutes. Garnish with parsley and extra Parmesan if desired. Serve immediately.