Put one tablespoon of oil inside a pan. 

Cook the steak in two small batches over medium-high heat until it is brown. So, this will take between two and three minutes, and you don’t need to cook the beef completely at this point. Then, remove the beef from the pan and set it aside.

Take all the ingredients for the sauce and combine them, except the cornstarch. 

Put the sauce ingredients in a pan and turn the heat to medium-high. Then, bring the sauce to a simmer.

Add the cornstarch with three tablespoons of broth or water and keep adding it to the sauce little by little while you whisk them together. Then, keep whisking it until you have reached the consistency you desire. 

Let everything simmer for two minutes. 

Add the beef and the vegetables to the pan and cook them until they are completely cooked.