Place the ground crab in a pot with a pinch of salt and enough water, stir well, and bring to a boil. Add chopped daikon radish for sweetness. Clean the snails thoroughly with white wine to remove odor. Wash the herbs, slice the lime and chili. Chop green onions, cilantro, and onion. Cut fried tofu into cubes.

When the crab broth boils, reduce the heat and gently stir so the crab forms curds on the surface. Carefully skim off the crab curds and set aside. In a pan, heat a little oil and sauté annatto seeds to release color, then remove the seeds. Sauté onions until fragrant, add tomatoes, and cook until just softened. Add the pork ribs to the crab broth and simmer until tender.

In another pan, heat oil and sauté ginger and garlic until fragrant, then add the snails and a splash of fish sauce. Stir briefly—do not overcook or the snails will become tough. Blend the soaked dried shrimp until fine, mix with ground pork, and add the egg. Season with a little bouillon powder and black pepper, and mix well. When the broth is boiling, add the fried tofu and tomatoes, then drop in small spoonfuls of the shrimp-pork mixture. As it cooks, the mixture will float to the surface.

Season the broth with 2 tablespoons fish sauce, 1 teaspoon fermented shrimp paste, bouillon powder, and a little tamarind juice to taste.
To serve, place noodles in a bowl, add tomatoes, snails, crab curds, and ladle the hot broth over. Top with green onions, cilantro, and black pepper. Serve with fresh herbs. Enjoy a flavorful and refreshing bowl of bún riêu ốc.