Cook spinach in chicken broth. Saute onion in butter in large saucepan until tender. Add flour and seasonings, stirring until smooth. Stir in spinach mixture. Cook, stirring constantly, until mixture just comes to a boil and is thickened. Stir in cream, crabmeat and relish. Heat through, do not boil. Note: This soup freezes well. Reheat slowly, don't boil. It's also nice with a can of crabmeat or small shrimp.