Toast the crumbs: In a large deep skillet or Dutch oven, melt the butter over medium heat. Add breadcrumbs and stir until golden and crisp, 2–3 minutes. Transfer to a bowl and set aside. This will be your crunchy topping.

Brown the chicken: Return the pot to medium-high heat and add olive oil. Pat the chicken dry and season with a pinch of salt and pepper. Cook in a single layer, stirring only occasionally, until lightly browned on the outside, 4–5 minutes. It doesn’t need to be cooked through yet. Remove to a plate.

Sauté aromatics: In the same pot, add the onion and a drizzle more oil if the pan looks dry. Cook until soft and translucent, about 3 minutes. Stir in the garlic, red pepper flakes, Italian seasoning, 1 teaspoon salt, and 1/2 teaspoon black pepper. Cook 30 seconds, just until fragrant.

Build the sauce base: Add tomato paste and cook, stirring, for 1 minute to caramelize slightly. Pour in the marinara and chicken broth, scraping up any browned bits from the bottom. Bring to a strong simmer.

Add pasta and chicken: Stir in the pasta and return the browned chicken (and any juices) to the pot. Make sure the pasta is mostly submerged. Adjust heat to maintain a steady simmer.

Simmer until tender: Cook uncovered, stirring every couple of minutes to prevent sticking, until the pasta is al dente and the chicken is cooked through, 10–12 minutes. If the pot looks dry before the pasta is done, add a splash of broth or water. You want a saucy consistency.

Finish creamy and cheesy: Reduce heat to low. Stir in the cream (if using), mozzarella, and Parmesan until melted and glossy. Taste and adjust seasoning with more salt or pepper as needed.

Top and rest: Sprinkle the toasted breadcrumbs over the pasta. Let it sit off heat for 2–3 minutes so the sauce thickens and the crumbs adhere slightly.

Garnish and serve: Shower with chopped basil or parsley and extra Parmesan. Serve hot right from the pot.