Cover the flank steak with cornstarch, making sure each piece is covered. Set aside.
Heat the canola oil in a large skillet over medium-high heat. Once the oil is hot, add the flank steak to the frying pan in a single layer, making sure that the pieces are not touching. Cook on 1-2 minutes per side until each side is browned. Cook in batches until all the flank steak is cooked. Set aside.
Add sliced yellow onion, whites of green onions, garlic, and ginger to the skillet and stir fry for about 3 minutes, until the onions are slightly softened but still have a little crunch. Add soy sauce, water, hoisin sauce, and brown sugar and stir. Add steak back to the pan along with the green parts of the onions. Remove from heat and serve.
Air fryer Instructions:
This Mongolian Beef can also be made in an Air Fryer. If Air Frying, coat the flank steak in corn starch and place in a preheated air fryer of 400 degrees Fahrenheit. Cook for 15 minutes, shaking the basket halfway. Prepare the sauce on the stove with the onion, garlic, ginger, soy sauce, water, hoisin sauce, and brown sugar.
After multiple tests, we preferred the stovetop version but wanted to share the Air Fryer version for anyone wanting to exclude the frying component of this recipe.
Freeze your steak before slicing it. It will make it easier and less likely to fall apart. Remember to cut against the grain.
Prep all of your ingredients before you start cooking. The dish comes together so quickly, so have everything to hand and ready to go.
If you have leftovers, they will keep in an airtight container in the fridge for 4 days. They can be reheated on the stove top or in the microwave.
The Mongolian beef will also freeze really well. Thaw it in the fridge overnight before reheating.