Nem cua bể is a delicious crab spring roll that is popular in Hanoi. The filling is made from minced crab meat, pork, mushrooms, and various spices. The mixture is then wrapped in rice paper and deep-fried until crispy. Nem cua bể is typically served with a dipping sauce made from fish sauce, lime juice, sugar, and garlic. These crispy and flavorful spring rolls are a favorite among locals and visitors alike.