- Heat the oven to 450 degrees. Brush a sheet pan all over with 1 tablespoon olive oil.
- Place the potatoes in a large pot and fill with enough water to cover by 1 inch; add 2 tablespoons salt. Bring to a boil over high heat, then lower and simmer, uncovered, for 15 to 18 minutes, until the potatoes are just fork tender. Pour into a colander to drain, then return the cooked potatoes to the pot off the heat to help any remaining moisture evaporate.
- Meanwhile, in a small bowl, whisk together the fish sauce, lime juice, rice vinegar, chile, soy sauce, sugar and garlic, then stir in the cilantro and scallions.
- Place the potatoes on the prepared sheet pan. Using the bottom of a measuring cup, gently smash each potato until it’s about ½-inch thick. Drizzle remaining 3 tablespoons olive oil over the potatoes and carefully flip to coat both sides in oil. Sprinkle with ½ teaspoon salt and roast for 30 to 40 minutes, until golden brown and crisp.
- Transfer the potatoes to a platter, sprinkle lightly with salt, then spoon the sauce on top. Garnish with cilantro leaves and serve hot.