Step 1

Place the noodles in a large, heatproof bowl and add boiling water to cover. Let stand, stirring once or twice and separating any strands that are sticking together, until the noodles are pliable, about 15 minutes, then drain. If the noodles are in very long strands, snip them with kitchen shears in several places to cut them into shorter lengths. Meanwhile, in a small bowl, beat the eggs with the ½ teaspoon fish sauce.

Step 2

In a 12-inch nonstick skillet over medium, heat 2 tablespoons oil until barely smoking. Add the egg mixture and swirl the pan to distribute the eggs in a thin, even layer. Cook until the surface is almost dry and the bottom is lightly browned, 30 to 60 seconds. Slide the omelet onto a cutting board; reserve the skillet. Let the omelet cool, then slice into thin ribbons.

Step 3

In the same skillet over medium, combine the sugar with the remaining 1 tablespoon oil. Cook, stirring occasionally to help the granules dissolve, until the sugar begins to turn golden; cook, swirling the pan instead of stirring, until the caramel is amber in color, 2 to 4 minutes. Remove from the heat and add the garlic and shallots. Return to medium and cook, stirring, until the mixture is fragrant, 45 to 60 seconds. Add the pork, oyster sauce, soy sauce and the remaining 2 tablespoons fish sauce. Cook, stirring and breaking the pork into small bits, until the meat is no longer pink, 2 to 3 minutes.

Step 4

Add the noodles, scallions and 2 tablespoons water. Cook, tossing often, until the noodles are tender and have absorbed the liquid, about 3 minutes. If the pan is dry but the noodles are not yet tender, add more water about 2 tablespoons at a time and continue to cook.

Step 5

Off heat, toss in the bean sprouts, half of the cilantro and half of the sliced omelet. Taste and season with salt. Transfer to a serving dish and garnish with the remaining cilantro and omelet. Serve with lime wedges, red pepper flakes and fried shallots (if using).