Prep the slow cooker. Lightly grease the crockpot insert or use a liner for easy cleanup.

Season the chicken. Place chicken in the crockpot. Sprinkle with Italian dressing mix, garlic powder, onion powder, crushed red pepper, black pepper, and salt.

Add liquid. Pour the chicken broth around the sides so you don’t rinse off the seasoning. If using mushrooms or sun-dried tomatoes, add them now.

Cook low and slow. Cover and cook on Low for 4–5 hours or High for 2.5–3.5 hours, until the chicken shreds easily with two forks.

Shred the chicken. Remove the chicken to a board and shred. Return it to the crockpot and stir to combine with the cooking liquid.

Add the creaminess. Add the cream cheese cubes and Parmesan. Cover and cook on Low for 15–20 minutes, then stir until smooth and creamy. If using spinach, stir it in now so it wilts.

Cook the rotini. Boil rotini in salted water according to package directions until al dente. Reserve 1/2 cup pasta water, then drain.

Combine. Stir the drained rotini into the crockpot. If the sauce seems thick, add a splash of reserved pasta water to loosen. For extra richness, stir in butter until melted.

Taste and finish. Adjust salt and pepper. Top with extra Parmesan and chopped parsley or basil. Serve hot.