Place bean sprouts in a large serving bowl. Top with cooked noodles. Fry garlic in oil until golden. Pour over noodles. In saucpan, heat chicken stock, pork, shrimp and fish sauce until it comes to a boil. Drop in lettuce leaves and immediately pour over the noodles. Add pork slices, green onions and cilantro. Sprinkle with sugar, peanuts and pepper flakes. Serve.