Roast the poblanos over an open flame or close under a hot broiler, turning regularly until blistered and blackened all over, 5 minutes for an open flame, 10 minutes for the broiler. Let cool until handleable, then rub the blackened skin off the chiles and pull out the stem and seed pod. Rinse the chile flesh to remove bits of skin and seeds. Cut into ¼-inch strips.
Scoop the potato cubes into a microwave-safe bowl, splash on a couple of tablespoons of water, cover (if using plastic wrap, poke a few holes), then microwave for about 3 minutes on high.
Heat the oil in a very large (12-inch) skillet over medium-high. When hot, sprinkle the beef generously with salt, then scoop it into the hot pan, spreading it into an uncrowded single layer. Brown the meat, cook, stirring frequently, until it is almost to the doneness you like—it should take about 4 minutes for medium rare. Remove to a plate.
Return the skillet to medium-high heat without washing. Scoop in the onions and potatoes and cook, stirring regularly, until the onions are richly browned, about 8 minutes. Add the garlic and stir for about a minute, until richly aromatic. Pour in the broth, beer or wine and the Worcestershire, sprinkle in a scant ½ teaspoon salt, reduce the heat to medium and let cook, stirring regularly and scraping up any sticky bits on the bottom of the skillet, until most of the liquid has reduced to a syrupy sauce, a couple of minutes..
Return the meat to the pan, add the chiles and sprinkle on the cilantro. When the meat has heated through, taste and season with additional salt, if necessary. Scoop the mixture onto dinner plates and you’re ready to eat.