Fry salt pork in soup kettle until crisp. Remove with slotted spoon and set aside. Sauté onions and garlic in fat until tender. Add spinach, cover, and simmer until wilted. Melt butter in separate saucepan. Add flour and stir over low heat until blended. Slowly add stock, stirring, and heat. Pour mixture into kettle and stir until smooth. Add clams and cream and heat. Do not boil.