Step 1: Bring a large pot of salted water to a rolling boil. Add the penne pasta and cook until al dente according to the package instructions. Before draining, reserve about half a cup of the pasta water. Drain the pasta and set aside.

Step 2: While the pasta cooks, season the chicken pieces generously with Cajun seasoning, salt, and black pepper. Make sure each piece is well-coated.

Step 3: Heat the olive oil and 1 tablespoon butter in a large skillet over medium-high heat. When hot, add the chicken in a single layer. Let it sear without stirring for a few minutes to develop a golden crust. Then stir occasionally, cooking until browned and cooked through, about 7–8 minutes.

Step 4: In the last minute of cooking, add half the minced garlic. Stir to combine and let the garlic release its aroma without burning. Remove the chicken and keep it warm.

Step 5: Reduce heat to medium. Melt the remaining 2 tablespoons of butter in the skillet. Add the remaining garlic and sauté for about 30 seconds until fragrant and golden, stirring frequently.

Step 6: Pour in the heavy cream, stirring constantly. Let it simmer gently for 2–3 minutes to thicken.

Step 7: Gradually add the mozzarella and Parmesan cheeses, stirring continuously until melted and the sauce is thick and creamy. Stir in Italian seasoning and crushed red pepper flakes to taste. Season with salt and pepper.

Step 8: Add the cooked penne pasta to the sauce. Toss gently to coat all the pasta. If the sauce is too thick, add reserved pasta water a little at a time until it reaches your desired consistency.