Heat oil in a medium-size nonstick saucepan over medium-high heat. Add onion, mushrooms and 1/4 teaspoon each of the salt and pepper to pot; cook, stirring occasionally, for 8 minutes or until softened.Advertisement
Stir in clam juice, broth and potato and bring to a boil. Reduce heat to medium-low and simmer for 20 minutes or until potato is tender.
Puree soup in a blender in batches until smooth. Return to pot and stir in remaining 1/4 teaspoon pepper, shrimp, crab, light cream and spinach; simmer for 10 minutes. Serve warm.