Prep the slow cooker base: Add the chicken breasts, chicken broth, garlic, onion powder, Italian seasoning, salt, and pepper to the slow cooker. Stir the liquid gently to distribute the seasonings.
2 pounds boneless, skinless chicken breasts (or thighs for extra tenderness), 3 cups low-sodium chicken broth, 4 cloves garlic, minced, 1 tsp onion powder, 1 tsp Italian seasoning, 1 tsp kosher salt (adjust to taste), ½ tsp black pepper
Layer in the cream cheese: Scatter the cream cheese cubes over the top. Don’t worry if they sit on top—the heat will melt them into the sauce later.
8 ounces cream cheese, cut into cubes
Cook low and slow: Cover and cook on Low for 3.5–4.5 hours or High for 2–3 hours, until the chicken is cooked through and tender.
Avoid lifting the lid too often; it drops the temperature and extends the cook time.
Shred or slice the chicken: Remove the chicken to a plate. Shred with two forks or slice into thin strips. Return it to the slow cooker.
Add the dairy finishers: Pour in the heavy cream and stir in the grated Parmesan.
If using, add the butter. Stir well to combine into a smooth, creamy sauce. Taste and adjust salt and pepper.
1 cup heavy cream, 1 cup freshly grated Parmesan cheese (plus extra for serving), 2 tbsp butter (optional, for extra silkiness)
Cook the pasta: While the sauce finishes blending, boil the fettuccine in salted water according to package directions until al dente.
Reserve 1/2 cup pasta water, then drain.
14 ounces fettuccine (or your favorite pasta)
Combine pasta and sauce: Add the cooked pasta to the slow cooker and toss to coat. If the sauce seems too thick, loosen with a splash of reserved pasta water until it clings nicely.
Optional add-ins: Stir in baby spinach until wilted, or fold in steamed broccoli, sautéed mushrooms, or chopped sun-dried tomatoes for extra texture and flavor.
Optional add-ins: baby spinach, steamed broccoli, sautéed mushrooms, or sun-dried tomatoes
Serve: Top with extra Parmesan and fresh parsley. Add cracked black pepper if you like a little bite.
Fresh parsley, chopped, for garnish