1 1/2 pounds beef sirloin tips or flank steak, cut into 3-inch pieces with the grain, then sliced ½ inch thick against the grain
Kosher salt and ground black pepper
3 tablespoons grapeseed or other neutral oil, divided
6 ounces fresh ginger, peeled and sliced into very thin coins (generous 1 cup)
4 medium garlic cloves, chopped
1 bunch scallions, cut into 2-inch lengths
3 tablespoons fish sauce
2 teaspoons white sugar
Note: The ginger is not just a flavoring here—it’s treated almost as a vegetable. A full cup of thinly sliced fresh ginger gives the dish substance; its spiciness and pungency is tamed by cooking. A mandoline makes quick work of slicing the ginger, but a chef’s knife works, too.
In a medium bowl, toss the steak with ½ teaspoon each salt and pepper. In a 12-inch skillet over high, heat 1 tablespoon of oil until barely smoking. Add half the meat in a single layer and cook until well browned on both sides, 2 to 3 minutes total, turning the slices only once. Transfer to a plate. Repeat with 1 tablespoon of the remaining oil and the remaining meat.
In the same skillet over medium, heat the remaining 1 tablespoon oil until shimmering. Add the ginger and cook, stirring frequently, until lightly browned, about 2 minutes.
Add the garlic and cook, stirring, until fragrant, about 30 seconds. Stir in the scallions, fish sauce and sugar, then return the meat and accumulated juices to the pan. Cook, stirring occasionally, until the liquid is slightly thickened and the ginger is tender, 2 to 4 minutes.
Taste and season with salt and pepper.