Beef and Stir-Fry 1 1 1/4 to 1 1/2 lb top sirloin steak 1 Tbsp cornstarch 2 Tbsp vegetable oil (preferably peanut) 1 Tbsp dark toasted sesame oil (optional) 3-4 green onions, cut on a diagonal, 1/2-inch apart, including the greens 2 cloves garlic, thinly sliced 2-3 hot chilis, preferably red serranos, seeded, sliced 1-inch nob of ginger, peeled, cut lengthwise into matchstick shapes 1/2 cup loosely packed, chopped cilantro
Chill the steak in the freezer for about 30 minutes. Remove the steak and slice it crosswise into 1/2″ strips. Then, cut each strip lengthwise , making long, strips of steak. Place the steak in a bowl. Whisk together the marinade and pour over the steak. Let the steak marinate at room temperature for 30 minutes or up to 4 hours in the fridge.
In a small bowl, mix the cornstarch with 2 tablespoons of cold water to make a slurry.
Heat the oil in a wok (vegetable oil plus dark sesame oil if using), or a large sauté pan, over high heat until it is nearly smoking. As the oil is heating up, pat the beef dry and separate it into small batches no larger than what can fit into the palm of your hand. Working in batches, sauté beef until just brown outside but rare inside, no more than 1 minute. Transfer beef to a bowl.
When all of the beef is cooked, put the chiles and garlic into the pan and stir-fry 30-45 seconds. Add the julienned ginger and cook for 30-45 seconds more.
Add the beef back to the pan. Add the cornstarch slurry. Add the scallions and mix everything together. Cook for 1 minute.
Turn the heat off and mix in the cilantro. Serve at once with steamed white rice.