This is my son’s favorite dish. If you don’t like spicy, you can use mild Italian sausage and cut down on the cayenne pepper.
Bring a large pot of salted water to a boil for the noodles. Cook noodles according to package directions; drain and set aside.
Sauté sausage and mushrooms in 2 Tb oil in a large sauté pan over medium-high heat until browned, about 5 minutes. Transfer to a bowl; set aside.
Combine chicken with seasonings, tossing to coat, then dust with flour. Sauté chicken in same sauté pan in 2 Tb oil over medium-high heat until nearly cooked through, about 5 minutes. Push chicken to one side of pan. Add tomato paste and garlic; sauté for 1 minute.
Deglaze with sherry, simmer until nearly evaporated, then add broth, Worcestershire, and reserved sausage-mushroom mixture. Bring to a simmer and reduce by half, about 5 minutes.
Off heat, stir in sour cream. Serve stroganoff over prepared egg noodles and garnish with scallions.