01 - Season the chicken pieces with salt and pepper.
02 - In a large, deep skillet or Dutch oven, melt 2 tbsp butter with olive oil over medium-high heat. Add the chicken pieces and sauté until lightly golden and just cooked through, 5–6 minutes. Remove chicken to a plate and set aside.
03 - In the same pan, add the remaining 1 tbsp butter. Add onion and sauté until softened, about 3 minutes. Stir in garlic and cook for 1 minute until fragrant.
04 - Add orzo and toast, stirring, for 1–2 minutes.
05 - Pour in the chicken broth and milk. Bring to a simmer, scraping up any browned bits from the bottom.
06 - Reduce heat to medium-low. Cover and cook, stirring occasionally, for 10–12 minutes, or until orzo is al dente and most of the liquid is absorbed.
07 - Stir in the peas and cooked chicken. Cook 2–3 minutes until peas are heated through and chicken is warmed.
08 - Remove from heat. Stir in Parmesan, parsley, and lemon zest. Season with additional pepper to taste. Serve immediately.