Begin by boiling a large pot of salted water. Cook the penne pasta according to the package instructions. Right before draining, add the shredded rotisserie chicken into the pot for the last minute to warm it through. This makes the chicken soft and juicy. Once ready, drain both the pasta and chicken together, then set them aside.

While the pasta is boiling, get started on the sauce. Heat olive oil and butter in a medium saucepan over medium heat. Add the minced garlic and stir for about 2 minutes until fragrant and golden. Be careful not to burn the garlic as it cooks quickly. Sprinkle in the red pepper flakes for a hint of spice and stir briefly. If using Italian seasoning, add it here to soften and blend into the sauce.

Now, for the fun part! Return the drained pasta and chicken to the pot (or use a large mixing bowl). Pour the garlic-butter sauce over it and toss to coat all the pasta evenly. Sprinkle in the freshly grated Parmesan cheese and chopped parsley, then mix once more until everything is well combined. The sauce should cling beautifully to the pasta, with every bite bursting with flavor.

Once combined, transfer the pasta to serving bowls or a platter, and garnish with a bit more Parmesan and parsley on top for presentation. This dish is best enjoyed while warm, with fresh bread or a crisp salad on the side.