Clean and slice the bell peppers and onions.
Slice the steak into even sized thinly cut strands. Add to a plate or bowl and toss with salt and pepper.
In a bowl, mix the soy sauce, brown sugar, water, minced garlic, cornstarch, and sesame seeds until well combined. Set aside.
Drizzle 2 tsp oil in a skillet and heat on medium high heat. Once hot, add the peppers and onions and sauté for about 5-6 minutes or until tender. Remove from the skillet, cover and set aside.
In the same skillet, 2 tsp oil and heat on high heat. Once hot add the seasoned steak and sear for 3-4 minutes or until browned.
Once the steak is cooked, add the sauteed veggies and sauce mixture to the skillet.
Toss and simmer for about an additional minute, allowing the sauce to thicken.
When the sauce has thickened, remove from heat and top with freshly chopped green onions and sesame seeds.
Serve immediately while still hot with desired sides.