In a medium bowl, whisk together the egg white, wine, 1 tablespoon of the soy sauce, 1 teaspoon of the sugar, the baking soda and ¼ teaspoon each salt and pepper. Slice the steak with the grain into 1-inch strips, then cut each crosswise into 1-inch pieces. Add to the egg white mixture and toss to coat. Let stand at room temperature for 1 hour (or cover and refrigerate up to 24 hours).

In a small bowl, stir together 1 tablespoon of the vinegar, 3 tablespoons water, the remaining 3 tablespoons soy sauce, remaining 2 teaspoons sugar and ¼ teaspoon salt; set aside.

Add the potatoes to a medium saucepan with water to cover by 1 inch. Stir in the remaining 2 tablespoons vinegar and ½ teaspoon salt. Bring to a boil over medium-high, then reduce to medium and simmer, stirring occasionally, until a fork inserted into the potatoes meets just a little resistance, 6 to 8 minutes. Drain in a colander, then transfer to a medium bowl. Sprinkle with the cornstarch and toss to coat.

In a 12-inch skillet over medium-high, heat 2 tablespoons of the oil until barely smoking. Add the potatoes in a single layer and cook, occasionally scraping up and turning them with a wide metal spatula, until browned and crisped all over, about 5 minutes. Add the onion and chilies; cook, stirring, until the onion is charred in spots but still crisp, about 2 minutes. Transfer the mixture to a large plate.

In the now-empty skillet over medium-high, heat the remaining 1 tablespoon oil until barely smoking. Add the beef in a single layer; cook without stirring for 1 minute. Using the metal spatula, scrape up and turn the pieces. Cook, occasionally flipping the beef, until browned all over, 4 to 6 minutes.

Sprinkle with 1 teaspoon pepper and cook, stirring, until fragrant, about 1 minute. Return the vegetable mixture to the pan; stir. Stir the soy sauce mixture to recombine, then add it to the pan; cook, stirring, until the beef and vegetables are lightly sauced, about 2 minutes. Off heat, taste and season with salt and pepper.