Pat chicken dry using paper towels. Cut chicken into 1- to 2-inch cubes and season with salt and pepper, if desired.
Heat oil in a large nonstick skillet over medium-high heat. Cook chicken for 2 minutes or until lightly browned (chicken will not be fully cooked at this point). Transfer chicken to a plate and set aside.
Add onions to pan and cook for 2 minutes. Add garlic and Italian herb seasoning. Stir in water and bouillon powder; bring to a boil.
Add fettuccini and stir gently. Reduce heat to medium and cover pan with lid. Cook for 6 to 7 minutes, stirring once.
Add chicken, broccoli and half and half, stirring to combine. Reduce heat to low, cover and continue cooking for 5 to 7 minutes or until chicken is cooked through and broccoli is tender.
Stir in Parmesan cheese until melted and sauce has thickened.
Garnish with additional Parmesan cheese, if desired.