Toss the sliced beef in a bowl with the cornstarch to coat. Heat the 1/2 tablespoon of oil in a wok over medium high heat. Cook the beef in the oil in 2 batches for 2-3 minutes and set aside in a bowl.
Add 1 tablespoon of oil to the wok and add the garlic and onions, cook for 2 minutes then add the sugar snap peas. Cook for 2-3 minutes then set aside with the beef.
Add the brown sugar, soy sauce, oyster sauce and black pepper to the wok. Bring to a boil and allow to reduce for 2-3 minutes. Add the beef and vegetables to the wok and toss in the sauce and cook for another 2-3 minutes. Serve over rice. Enjoy!