1Cut the skirt steak into thinner bite-sized pieces against the grain.
2In a bowl, add the steak and coat it with about a quarter to a third of a cup of corn starch, two tablespoons of soy sauce, and a drizzle of sesame oil. Mix well with your hands.
3In another bowl, make the stir fry sauce by mixing half a cup of water, half a cup of soy sauce, half a cup of brown sugar, and a drizzle of sesame oil.
4Heat a pan and add some oil.
5Add half of the marinated beef to the pan, and sear until browned on both sides. Remove from the pan and set aside.
6Add a little more oil to the pan and saute the red onion until slightly softened.
7Add the minced garlic, red Holland pepper, and fresh chopped ginger to the pan and let it get fragrant.
8Pour the stir-fry sauce into the pan and let it bubble away.
9Add the seared beef back to the pan along with any accumulated juices.
10Add the green onion stems and stir to combine everything well.
11Serve the Mongolian beef over rice and garnish with sesame seeds.