How to Make It
In a large saucepan, heat the oil. Add the shallots and garlic and cook over moderately high heat, stirring occasionally, until golden, 3 to 5 minutes. Stir in the shrimp paste and tomato paste and cook, stirring, until fragrant, about 30 seconds. Add the chicken stock and water and bring to a boil. Reduce the heat to moderate, add the tomatoes and simmer until just starting to pop, about 8 minutes. Using a wooden spoon, lightly crush some of the tomatoes on the side of the pan. Stir in the fish sauce and season the soup lightly with salt.
In a medium bowl, beat the eggs with the chile-garlic paste and a generous pinch of salt. Add the crab and pork and, using a fork, stir the mixture well to break up the meat.
Bring the soup to a rolling boil over high heat. Stir in a circular motion and pour the egg mixture into the center of the swirl. Stop stirring and simmer the omelet in the soup over moderate heat for 6 minutes, then turn off the heat and stir to distribute the omelet throughout the soup.
In a large heatproof bowl, cover the vermicelli with boiling water and let stand until softened, about 10 minutes. Drain well. Divide the vermicelli and bean sprouts among 4 bowls. Ladle the soup on top and serve with lime wedges and mint, cilantro and basil leaves.
Fermented shrimp paste is available at Asian markets and from amazon.com.