In a large saucepan, heat butter over medium-high heat. Add onion; cook and stir 2-4 minutes or until tender. Add potatoes, corn, broth, 1 cup cream, green onions, salt and pepper; bring to a boil. Reduce heat; simmer, covered, 12-15 minutes or until potatoes are tender., In a small bowl, mix flour and remaining cream until smooth; stir into soup. Return to a boil, stirring constantly; cook and stir 1-2 minutes or until slightly thickened. Stir in parsley.