Begin by setting up your work area with all the ingredients laid out.

Shred the rotisserie chicken gently using your fingers or two forks for a natural texture.

In a large pot, boil water with a pinch of salt. Add the penne pasta and cook until al dente according to the package instructions. Drain and set aside.

In the same pot, blanch the broccoli florets in boiling water for 2-3 minutes until they’re bright green and tender-crisp. Quickly transfer them to an ice bath to halt cooking. Drain and set aside.

Heat olive oil in a large skillet over medium heat. Add diced onion and sauté until translucent and slightly caramelized, around 5 minutes. Introduce minced garlic, letting its aroma fill the air for about 1 minute.

Add butter to the onion and garlic mix, stirring until melted. Pour in heavy cream and chicken broth, stirring consistently to maintain a silky, smooth texture. Let simmer for 3 minutes.

Gradually whisk in freshly grated Parmesan and shredded mozzarella until completely melted. Add Italian seasoning, garlic powder, and optional red pepper flakes, stirring to combine.

Introduce the shredded chicken and blanched broccoli into the skillet, folding gently to coat with the sauce while preserving their textures.

Add cooked pasta to the skillet, tossing with tongs until evenly mixed. Adjust seasoning as needed. Serve hot, garnishing with extra Parmesan if desired.