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

In a large pot, bring salted water to a boil. Add your penne or rigatoni pasta, cooking it for 2 minutes less than the package suggests. Drain the pasta, but reserve a cup of the pasta water.

Heat a generous splash of olive oil in a large skillet over medium-high heat. Add the diced chicken breast and sauté for about 6-8 minutes until golden brown and cooked through.

In the same skillet, add unsalted butter and let it melt over medium heat. Once melted, add minced garlic and cook for about 1-2 minutes until fragrant. Gradually pour in heavy cream and whole milk, allowing to simmer until it thickens.

Stir in basil pesto and grated Parmesan cheese into the creamy mixture, blending until smooth.

Toss the sautéed chicken, drained pasta, and baby spinach into the skillet, combining gently until coated with creamy sauce.

Transfer the creamy mixture into the greased baking dish, spreading it out evenly. Top with shredded mozzarella and extra Parmesan.

Place the baking dish in the preheated oven and bake for 20-25 minutes until cheese is bubbling and golden.

Let the dish rest for about 5 minutes before serving.