Step 1

Place 1½ lb. boneless rib-eye steak, cut into 1" cubes, 2 Tbsp. plus 1 tsp. cornstarch, 1 Tbsp. dark soy sauce, 1 Tbsp. soy sauce, and 1 Tbsp. unseasoned rice vinegar in a medium bowl; toss to coat.

Step 2

Stir 1 tsp. freshly ground pepper, remaining 4 tsp. dark soy sauce, remaining 1 Tbsp. soy sauce, remaining 1 Tbsp. unseasoned rice vinegar, and ½ cup water in another medium bowl to combine; set dressing aside.

Step 3

Warm 1 Tbsp. vegetable oil in a large skillet or wok over medium-high heat. Place steak with marinade in pan, arranging in a single layer as much as possible. Cook, undisturbed, until browned underneath, about 2 minutes. Turn over and cook until browned on other side, about 2 minutes. Transfer steak to bowl with reserved dressing and toss to coat. Wipe out skillet.

Step 4

Heat remaining 1 Tbsp. vegetable oil in same skillet over high. Cook 1 medium onion, thinly sliced, stirring constantly, until fragrant, about 30 seconds. Add 8 finger hot peppers or cayenne chiles (about 8 oz.), sliced 1" thick, one 2" piece fresh ginger, peeled, finely chopped, and 5 garlic cloves, finely chopped, and cook, stirring often, until softened and starting to char, about 5 minutes. Reduce heat to medium, add steak with dressing, and toss to combine. Stir in up to ¼ cup water to loosen sauce if needed. Taste stir-fry and season with kosher salt if needed.

Step 5

Transfer steak mixture to a shallow bowl; serve with steamed white rice.