Begin by filling a large pot with water and setting it over high heat. Once the water reaches a rolling boil, generously salt it and add the penne pasta. Cook for about 8–10 minutes, stirring occasionally until al dente. In the final 3 minutes of cooking, gently add the broccoli florets.

Once cooked, carefully reserve about 1 cup of the starchy pasta water and then drain the pasta and broccoli together.

In a large skillet over medium-low heat, combine olive oil and butter. Once hot, add diced onion and sauté for 3–4 minutes until softened. Stir in minced garlic and cook for 30 seconds.

Reduce heat and pour in heavy cream and chicken broth. Allow to simmer for 2–3 minutes without boiling.

Remove the skillet from heat and whisk in Parmesan and mozzarella until smooth. Season with Italian seasoning, garlic powder, and salt and pepper to taste. Optionally, sprinkle in red pepper flakes.

Gently return the drained pasta and broccoli to the skillet and fold into the sauce. Add the shredded chicken and stir to combine.

Gradually add the reserved pasta water, stirring until the sauce reaches your preferred thickness.

Garnish with extra Parmesan or freshly cracked black pepper, and serve warm.