Preheat the oven to 375°F (190°C). Prepare a baking dish by spraying it with nonstick cooking spray.

Cook the pasta shells in a large pot of salted water until al dente, about 8–10 minutes.

Sauté minced garlic in olive oil over medium heat until fragrant, about 1 minute. Add the chopped chicken, cooking until it’s no longer pink, about 5 minutes. Stir in the fresh spinach until wilted, then mix in the ricotta and half of the mozzarella.

Combine the heavy cream and freshly grated Parmesan cheese in a saucepan over medium heat. Stir until smooth, seasoning with salt and pepper to taste.

Stuff each cooked shell generously with the chicken-spinach mixture. Arrange them snugly in the prepared baking dish, then drizzle the creamy sauce over the top. Sprinkle the remaining mozzarella cheese on top.

Bake uncovered for 25–30 minutes until the cheese is bubbly and golden brown.