Cook noodles according to package directions, adding broccoli the last 5 minutes of cooking. Drain; return noodles and broccoli to pan.
Meanwhile, stir together the sour cream, horseradish, and dill in a small serving bowl; cover and chill until serving time.
Trim fat from beef. Cut beef into bite-size strips. Cook half of the beef, all of the onion, and garlic in hot oil in a large skillet until onion is tender and beef is of desired doneness. Remove from skillet. Add remaining beef; cook and stir until beef is of desired doneness. Return all meat to skillet; sprinkle flour and black pepper over meat. Stir to coat.
Stir in broth, tomato paste, and Worcestershire sauce. Cook and stir until mixture is thickened and bubbly. Cook and stir 1 minute more. Divide noodle-broccoli mixture among four bowls. Spoon beef mixture on top of noodle mixture. Top with one or two spoonfuls or two of the sour cream mixture. Makes 4 servings.