Melt 2 tablespoons butter in a large skillet over medium high heat. Add broccoli and onion; cook 3 minutes, stirring frequently. Remove from skillet.
Melt remaining 2 tablespoons butter in skillet. Add chicken, half at a time to skillet. Cook 3 to 5 minutes per batch, stirring frequently, until chicken is no longer pink. Return all chicken and vegetables to skillet.
Stir milk gradually into cornstarch in a small bowl. Pour into skillet. Add bouillon cube. Bring to boil over medium heat, stirring constantly; boil 1 minute. Remove from heat.
Stir in lemon juice and parsley, if desired. Toss with pasta. Season with salt and pepper to taste.
Nutritional Claims: Source of fibre, Excellent source of protein, Source of potassium, Source of calcium, Source of iron