Bring a large pot of salted water to a boil. Add spaghetti and cook according to package instructions until al dente (about 8-10 minutes). Reserve 1 cup of pasta water before draining.

While the pasta cooks, season the chicken breasts generously with Cajun seasoning.

In a large skillet, melt 2 tablespoons of butter over medium-high heat. Once hot, add the chicken and cook for 5-7 minutes per side, until cooked through and juices run clear. Remove from the skillet and let rest before slicing.

In the same skillet, lower the heat to medium and add remaining butter. Sauté minced garlic until fragrant (about 30 seconds).

Pour in heavy cream, stirring constantly. Allow it to simmer on low for about 3-5 minutes until slightly thickened.

Add mozzarella cheese to the sauce, stirring until melted and creamy. If it’s too thick, add reserved pasta water a tablespoon at a time.

Toss the cooked spaghetti with the sauce until well coated, and serve with sliced chicken on top.