In a large pot of salted boiling water, cook the penne pasta according to package directions until al dente. In the last 2 minutes of cooking, add the broccoli florets to the same pot. Drain and set aside.

While the pasta cooks, heat olive oil in a large skillet over medium-high heat. Season the chicken pieces with salt and pepper, then add them to the pan. Sauté until golden brown and cooked through, about 5–7 minutes. Remove and set aside.

In the same skillet, reduce heat to medium. Add minced garlic and red pepper flakes (if using), and sauté for about 1 minute until fragrant.

Pour in the chicken broth and heavy cream. Stir and let simmer for 2–3 minutes to slightly reduce.

Return the cooked chicken to the skillet, then add the drained pasta and broccoli. Toss everything together until well coated. Stir in Parmesan cheese and lemon zest if using.

Taste and adjust seasoning with extra salt, pepper, or cheese if desired. Serve hot, optionally garnished with extra Parmesan and fresh herbs.