In soup pot over medium high heat, cook fennel and onion with olive oil until soft, 5 min. Add garlic and cook 1 min more. Add lemon juice, zest, salt, pepper, paprika and broth and bring to a boil. Add orzo and cook until al dente, 5 min. Add cream, spinach and chicken: heat to a simmer. Remove from heat and divide amongst serving bowls. In small skillet heat butter, cayenne, thyme and sage until sizzling and leaves begin to crisp. Divide herb butter over soup in bowls and top with sprinkle of Parmesan, fennel fronds and more lemon zest, if desired.