01 - Season the diced chicken with salt and black pepper, coating evenly.
02 - Heat olive oil in a large, deep skillet over medium-high heat. Add chicken and cook until browned and cooked through, about 5 minutes. Remove chicken to a plate and set aside.
03 - In the same skillet, add onion and red bell pepper. Sauté for 2–3 minutes until softened. Add garlic and cook for another 30 seconds until fragrant.
04 - Stir in risoni pasta and Italian herbs; toast for 1 minute, stirring frequently to coat and lightly toast the grains.
05 - Pour in chicken broth and milk. Bring to a simmer, scraping up any browned bits from the pan bottom.
06 - Reduce heat to medium-low. Cover and simmer for 10–12 minutes, stirring occasionally, until risoni is tender and most of the liquid has been absorbed.
07 - Return the cooked chicken to the skillet, add spinach, and stir until wilted, about 1 minute.
08 - Remove from heat. Stir in mozzarella and Parmesan cheese until melted and creamy. Sprinkle with red pepper flakes if desired.
09 - Taste and adjust seasoning. Serve hot, garnished with extra Parmesan if desired.