# Easy Mongolian Beef Mongolian beef is thin-sliced steak seared until crisp at the edges and tossed in a sweet, garlicky soy sauce. It is a takeout favorite that comes together faster than delivery. A light cornstarch coat gives the beef a silky texture and helps the sauce cling. Serve it over steamed rice or noodles with a green vegetable on the side. - Total time: 27 min (prep 15 min, cook 12 min) - Serves: 4 - Per serving (estimated): 440 kcal, 30 g protein - Cuisine: Chinese. Category: Main course. Diet: dairy-free, high-protein. ## Ingredients - 450 g flank steak, sliced thin against the grain - 3 tbsp cornstarch - 3 tbsp neutral oil, divided - 4 cloves garlic, minced - 1 tbsp fresh ginger, grated - 60 ml low-sodium soy sauce - 60 ml water - 1/3 cup brown sugar, packed - 1 tbsp rice vinegar - 1 tsp toasted sesame oil - 4 scallions, cut into 2-inch pieces - 1 tsp sesame seeds ## Method 1. Put the sliced steak in a bowl and toss with 2 tablespoons of the cornstarch until every piece is lightly coated. Let it sit 5 minutes. 2. Whisk the soy sauce, water, brown sugar, rice vinegar and sesame oil in a small bowl until the sugar dissolves. Stir the remaining 1 tablespoon cornstarch into 1 tablespoon cold water in a second small bowl and set both aside. 3. Heat a 12-inch (30 cm) skillet or wok over high heat until a drop of water sizzles instantly. Add 2 tablespoons oil. 4. Add half the beef in a single layer. Sear 1 to 2 minutes without moving it until deeply browned on the bottom, flip, and cook 30 seconds more. Move to a plate. Repeat with the rest. 5. Lower the heat to medium. Add the remaining 1 tablespoon oil, garlic and ginger. Stir 20 seconds until fragrant but not browned. 6. Pour in the sauce and bring to a simmer, 1 minute. Stir the cornstarch slurry, add it, and simmer 1 to 2 minutes until the sauce coats a spoon. 7. Return the beef and any juices to the pan along with the scallions. Toss 1 minute until glossy and the beef reaches 145°F (63°C). Sprinkle with sesame seeds and serve over rice. ## Why it works - Slicing flank steak thin against the grain cuts the long muscle fibers short, so each bite is tender instead of chewy. - The cornstarch coating forms a thin crust that browns quickly and protects the beef from drying out in the hot pan. - Searing in two batches keeps the pan hot enough to brown rather than steam the meat. - A cornstarch slurry added to a simmering sauce thickens it in about a minute into a glossy glaze. ## The science - **Cutting against the grain.** Muscle fibers in flank steak run in one direction like long ropes. Slicing across them chops those ropes into short pieces, so your teeth do less work. Slicing with the grain leaves long strands that stay chewy no matter how well you cook them. - **Starch thickening.** Cornstarch granules swell and burst when heated in liquid, trapping water and thickening the sauce. They need to reach a simmer to work, and the sauce turns glossy rather than cloudy once the starch is fully cooked. ## Tips - Freeze the steak for 20 minutes first; it slices much thinner and more evenly when firm. - Have everything measured before you start, because the cooking moves fast. - Always stir a slurry right before adding it, since the starch settles to the bottom. ## Mistakes to avoid - Slicing with the grain, which makes tough, stringy beef; look for the lines and cut across them. - Crowding the pan, which steams the beef gray; sear in two batches. - Adding cornstarch slurry to a sauce that is not simmering, which leaves it thin; bring it to a bubble first. ## Variations and swaps - Add 1 teaspoon chili flakes or a spoon of chili garlic sauce for heat. - Toss in broccoli florets, blanched for 2 minutes, to make it a one-pan meal. - Use thinly sliced chicken thighs instead, cooked to 165°F (74°C). - Swap flank steak for sirloin or skirt steak, both sliced thin against the grain. - Swap brown sugar for honey or dark brown sugar for a deeper flavor. - Swap rice vinegar for apple cider vinegar in a pinch, which is slightly sharper. ## Storage Refrigerate within 2 hours in an airtight container for up to 3 to 4 days. Reheat in a skillet with a splash of water until steaming, at least 165°F (74°C). ## FAQ **What cut of beef is best for Mongolian beef?** Flank steak is the best choice because it is lean, flavorful and slices thin. Sirloin and skirt steak also work well, as long as you slice them thin against the grain. **How do I make the beef tender?** Slice it thin against the grain and coat it in cornstarch before searing. Cook it quickly over high heat and do not overcook; 2 to 3 minutes total is enough. **Why is my Mongolian beef sauce watery?** The cornstarch slurry did not get to a full simmer, or there was not enough of it. Bring the sauce to a bubble and cook 1 to 2 minutes until it coats a spoon. **Is Mongolian beef actually from Mongolia?** No. It is a Chinese-American takeout dish, popularized by Taiwanese barbecue restaurants in the 1970s. The name refers to the style of cooking rather than the origin. **What do you serve with Mongolian beef?** Steamed jasmine rice is classic. Add steamed broccoli, sauteed green beans or a crisp cucumber salad to balance the sweet, rich sauce. --- Source: https://cookingscientist.com/recipes/mongolian-beef (Cooking Scientist). Learn the science of cooking in the Cooking Scientist app for iPhone and iPad: https://apps.apple.com/app/id6830326846