Preheat your oven to 400°F (200°C) and grease a 9x13-inch baking dish.

Bring a large pot of salted water to a boil. Cook pasta until al dente, about 2 minutes less than package instructions.

In a skillet, heat olive oil over medium-high heat. Season chicken with salt and pepper and cook until golden brown, about 5–6 minutes. Cut into bite-sized pieces.

In the same skillet, melt butter, add garlic, and sauté for 1-2 minutes. Stir in cream and milk, simmer for 2-3 minutes.

Add pesto and Parmesan cheese, mixing until smooth. Combine chicken, pasta, and optional spinach in a bowl. Pour sauce over and toss.

Transfer mixture to prepared baking dish, top with mozzarella and extra Parmesan.

Bake uncovered for 20–25 minutes until golden brown.

Let it rest for 5 minutes before serving.