Prep Oven & Pan: Preheat oven to 400°F (200°C) and generously grease a 9×13-inch baking dish.
Blanch & Chop Broccoli: Slice broccoli into quarters. Cook in boiling water for 2 minutes until bright green, then cool and chop into bite-sized pieces.
Boil Pasta: Cook penne until al dente. Drain well.
Brown Chicken: Heat olive oil in a large skillet. Add cubed chicken and cook 6–7 minutes, turning occasionally, until browned but not fully cooked. Remove from skillet.
Sauté Aromatics: Melt butter in the same skillet. Add onion and garlic, cooking 3–4 minutes until soft and fragrant.
Build Roux & Season: Sprinkle in flour, Italian seasonings, salt, and pepper. Stir 1–2 minutes until flour is lightly toasted.
Create Cream Sauce: Pour in milk and chicken stock, scraping the pan. Bring to a simmer. Add half-and-half, browned chicken, and broccoli. Simmer briefly to coat ingredients.
Combine in Baking Dish: Transfer mixture to the prepared dish and stir in cooked pasta until evenly combined.
Top with Cheeses: Scatter Parmesan and mozzarella evenly over the top.
Bake: Bake 15–20 minutes until cheese is bubbly and golden. Let rest 5 minutes before serving.
Notes & Tips
