Boil a large pot of salted water over high heat. Cook rigatoni according to package instructions until al dente, about 8-10 minutes. Reserve ½ cup pasta water, then drain and set aside.

In a large skillet, melt 1 tablespoon butter over medium-high heat. Season chicken with salt and pepper, add to the skillet, and sear for 6-8 minutes until golden brown and cooked through. Transfer to a cutting board to rest.

Reduce heat to medium and add remaining 2 tablespoons of butter. Once melted, add minced garlic and sauté for 1-2 minutes until fragrant.

Pour in heavy cream while stirring, allowing to simmer for 3-4 minutes until slightly thickened. Gradually whisk in Parmesan until melted and smooth.

Return sliced chicken and drained rigatoni to the skillet. Toss to coat with the sauce, adding reserved pasta water as needed.

Simmer for an additional 2-3 minutes to meld flavors. Garnish with chopped parsley and extra Parmesan before serving.