Bring a large pot of salted water to a boil. Add the noodles and cook as the label directs, then drain. Meanwhile, melt 2 tablespoons butter in a large skillet over medium-high heat. Add the onion and cook until slightly soft, about 2 minutes. Add the mushrooms and cook, stirring, until they begin to brown, about 2 minutes. Add the remaining 1 tablespoon butter, the chicken, flour, paprika, 1 teaspoon salt and 1/4 teaspoon pepper. Cook, stirring, until the chicken browns, about 3 minutes. Add the chicken broth and Worcestershire sauce and bring to a gentle simmer; cook until thickened, about 5 minutes. Stir in the sour cream and season with salt and pepper. Continue simmering gently until the chicken is cooked through, about 2 more minutes. Divide the noodles among plates. Top with the chicken mixture, parsley, some sour cream and paprika.