First, thinly slice the sirloin steak into strips and add to a large bowl. Then season with salt, black pepper, ground ginger, ground coriander, and onion powder. Toss to ensure every piece of steak is coated.
Combine the sauce ingredients in a medium bowl - brown sugar, Worcestershire sauce, soy sauce, brown sugar, and freshly grated ginger. Mix together and set aside.
Add one tablespoon of sesame oil to a large skillet and heat oil over medium-high heat. Once the oil is hot, add beef strips in a single layer and cook for 2-3 minutes on each side. Place on a plate with a paper towel to drain any excess oil. Pro tip: cook beef in batches to ensure that the pan doesn't get overcrowded.
Add remaining tablespoon of sesame oil to the pan and add sliced green and red peppers and onions. Saute in the pan until the peppers begin to soften, about 5 minutes. Reduce heat to medium, add garlic, and pour in the sauce.
In a small bowl, mix together cornstarch and 2-4 tablespoon of water until smooth. Pour cornstarch mixture and beef broth into the pan and simmer until the sauce begins to thicken, about 4-5 minutes. Stir continuously.
Add steak back into the skillet and cook for another 1-2 minutes. Serve over white rice or brown rice and top with sesame seeds. Enjoy!