In a bowl combine the peanut butter, water, chili flakes, sesame oil and 4 tablespoons of soy sauce. Mix well. Boil the spaghetti and drain. Toss the spaghetti with the peanut sauce and serve. Marinate the beef with the garlic powder and the soy sauce and let stand 1/2 hour. Blanch and shuck the head of broccoli. Saute in wok with sweet and sour sauce and the marinated beef. Serve when beef is thoroughly cooked.