Season chicken, if desired, with salt and pepper. Heat 1 tablespoon (15 mL) oil in large nonstick skillet over medium-high heat and cook chicken, stirring occasionally, until thoroughly cooked, about 5 minutes; remove and set aside.
Heat remaining 1 tablespoon (15 mL) oil in same skillet over medium heat and cook garlic, stirring, until garlic is fragrant, about 30 seconds. Add 1 cup (250 mL) water and 1 cup (250mL) milk and bring to a boil. Stir in Knorr Sidekicks® Creamy Bacon Carbonara Pasta Side Dish and cook covered according to package directions, adding rapini during the last 5 minutes of cook time.
Stir in chicken and serve garnished, if desired, with toasted chopped walnuts and grated Parmesan cheese.