Heat the oven to 425°F with a rack in the middle position. In a medium bowl, whisk the eggs. Reserve a couple tablespoons scallions for garnish.
In a large bowl, use your hands to thoroughly mix the pork, the remaining scallions, garlic, fish sauce and ¼ teaspoon pepper. Add the eggs and mix with a silicone spatula, breaking the pork mixture into bits, until the ingredients are well combined and no large clumps of meat remain.
In a 12-inch nonstick oven-safe skillet over medium-high, heat the oil until barely smoking. Add the pork-egg mixture; using the silicone spatula, break up any large bits of pork and evenly distribute the meat. Cook until the bottom is browned and set enough that you can lift an edge of the omelet with the spatula, about 3 minutes. Transfer the skillet to the oven and cook until the omelet is set in the center, 3 to 4 minutes.
Remove the skillet from the oven (the handle will be hot). Run the spatula around the edges of the omelet and underneath it to loosen, then carefully slide onto a platter. Alternatively, to serve the omelet browned side up, carefully invert it onto a platter. Serve warm or at room temperature, sprinkled with the reserved scallions and cut into wedges.
