Slice the beef thinly against the grain, about ¼-inch thick. If your beef is soft, pop it in the freezer for 20–30 minutes first—it makes slicing much easier.
In a large bowl, combine the lemongrass, garlic, ginger, fish sauce, oyster sauce, soy sauce, sugar, honey, oil, and black pepper. Mix until the sugar is mostly dissolved.
Add the beef and toss thoroughly to coat every piece. Cover and refrigerate for at least 4 hours, but overnight is where the magic happens.
Preheat your grill to medium-high heat (about 400°F / 200°C). Lightly oil the grates. Grill the beef for 2–4 minutes per side, depending on thickness, until nicely charred around the edges and just cooked through.
Let the beef rest for a few minutes before serving. Pile it over hot jasmine rice, vermicelli noodles, or stuff it into a bánh mì with pickled daikon and carrots.
