Gather all ingredients.
Heat oil in a large Dutch oven over medium. Add onion and cook, stirring occasionally, until softened, 2 to 3 minutes. Add garlic and cook, stirring occasionally, until fragrant, about 30 seconds. Stir in orzo and cook, stirring constantly, until lightly toasted, about 1 minute.
Stir in heavy cream, broth, about 1 teaspoon lemon zest, and 3 tablespoons lemon juice; bring to a simmer over medium heat, stirring occasionally to prevent the bottom from sticking, about 3 minutes. Reduce heat to medium-low; simmer, stirring constantly, until orzo is tender and mixture is thickened, 8 to 10 minutes.
Stir in chicken and spinach until spinach wilts, about 1 minute. Remove from heat. Stir in fontina, Parmesan, parsley, pepper, and salt until creamy, about 30 seconds.
Serve immediately topped with additional Parmesan and parsley.