If the chicken tenders are frozen, run them under hot water to remove any packaging. Place the tenders on a microwave-safe plate and microwave on high for 2 minutes to begin defrosting.
While the chicken defrosts, heat the oil over medium heat in an extra deep, 12-inch skillet. Add the onion, mushrooms and garlic. Stir from time to time. Cut the chicken tenders into bite-size chunks, and add them to the skillet. Raise the heat to medium high. Cook 6 minutes or until no longer pink in the center, stirring from time to time.
Meanwhile, place the fettuccine in 2 1/2 quarts of already-boining unsalted water and cook. When the noodles have cook 7 minutes, add the broccoli florets to the noodle pot. Bring the noodles back to a boil, and continue to cook 4 to 5 minutes or until noodles are tender.
When the chicken has cooked through, add the sherry and cook 1 minute. Add the mushroom soup, reduce the heat to medium-low and stir until well-combined. Add the Worcestershire sauce and sour cream and stir until well-combined. Add black pepper to taste.
Drain the noodles and broccoli. Place some noodles on each plate, and top each serving with the chicken mixture, and serve at once.