====== Pho Bo (Hanoi Beef Soup) ====== (Adapted from ''Simple Art of Vietnamese Cooking,'' by Binh Duong and Marcia Kiesel, Prentice Hall Press, 1991) * 1 pound rice vermicelli * * 8 cups Vietnamese-style beef stock (recipe follows) * * 3/4 pound lean beef, preferably round, sliced paper thin * * 1/2 cup mung-bean sprouts * * 1/2 cup cilantro leaves * * 1/2 cup small basil leaves, chopped * * 2 scallions, chopped * * 1 lime, cut into wedges * * 3 fresh red Thai chilies, seeded and chopped * * Bottled fish sauce for serving * * Freshly ground black pepper. 1. Place the vermicelli in a large bowl and cover with cold water. Allow to soak until pliable, about 30 minutes. Drain. 2. Place the stock in a large pan and bring it to a boil. Have either 4 very large or 6 slightly smaller individual soup bowls ready. Put a handful of vermicelli into a strainer that will fit in the pan and dip the strainer into the hot stock. Swirl the vermicelli until tender but still a little chewy, about 20 seconds. Shake the vermicelli dry and place it in a soup bowl. Repeat with the remaining noodles. 3. Divide the beef, sprouts, cilantro, basil and scallions among the bowls. Ladle the hot stock into the bowls and squeeze a lime wedge over each. Serve with the chilies, fish sauce and black pepper on the side. Yield: 4 to 6 servings.