Heat cooking oil in a nonstick skillet until hot, but not scorched. Over high heat, cook beef strips until browned. Sprinkle salt over beef while it cooks.
Once browned, remove beef from skillet but leave juices in pan. Over high heat, cook peppers, garlic, onions, ginger, water chestnuts, and salt together. Cook for about 5 minutes, until vegetables are crisp tender.
Add beef bullion granules to 3/4 cup of hot water and stir to dissolve. Pour bullion over vegetables in skillet. Turn heat down to medium.
Stir cornstarch into cold water until dissolved, then stir in sugar, and soy sauce. Add beef back to skillet and stir to combine. Turn heat down to medium-low and slowly pour soy sauce and corn starch mixture into skillet, evenly coating meat and vegetables. As liquid begins to heat, the cornstarch will thicken, making a glossy sauce that coats everything.
Cook just a little longer until meat and vegetables are cooked to your liking. Serve over white or brown rice, with extra soy sauce and sesame seeds to garnish. Enjoy!