Wash and trim spinach, leaving water that clings to leaves. Place in Dutch oven. Bring to boil. Reduce heat and steam just until wilted, about 4 minutes. Drain and chop; set aside.
Melt butter in large saucepan over medium heat. Whisk in flour until smooth. Gradually add cream and milk. Bring to boil; cook and stir 2 minutes or until thickened. Stir in onion, salt and pepper. Fold in spinach; heat through.