Bring a large pot of salted water to a boil. Cook the penne pasta according to package directions until al dente.

In the final three minutes of cooking, toss in the broccoli florets directly into the boiling pasta water.

Before draining, scoop out 1 cup of the starchy pasta water and set it aside. Then, drain the pasta and broccoli together and place them back in the pot.

In your largest skillet, heat olive oil and butter over medium-low heat. Add diced onion and cook for about 4-5 minutes until softened, then introduce the minced garlic, cooking for an additional 30 seconds until fragrant.

Pour in the heavy cream and chicken broth, gently bringing the mixture to a simmer for 2-3 minutes—watch for those little bubbles forming around the edges but keep it from boiling.

Remove the skillet from the heat. Whisk in the Parmesan and mozzarella until it’s all smooth. Season with the Italian seasoning, garlic powder, salt, pepper, and optional red pepper flakes.

Gently add the drained pasta and broccoli to the creamy sauce. Use tongs to toss them together evenly. Finally, fold in the shredded rotisserie chicken.

Adjust the consistency by adding reserved pasta water, two tablespoons at a time, until you achieve that creamy, glossy look. For that special touch, stir in a chilled knob of butter just before serving to elevate the richness.