Marinade the beef in sugar, soy sauce and the cornflour slurry for 15 minutes.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the beef until 70% done, about 3-4 minutes. Set aside.
Heat the same frying pan with 1 tablespoon oil over high heat. Stir-fry the garlic until aromatic, 2-3 minutes. Add the onion and salt, cook until soft, 3-4 minutes.
Stir in the carrots, baby sweetcorn and black soy sauce. Mix well. Add the oyster sauce, sugar, soy sauce, hoisin sauce, chicken stock granules, black pepper and water. Allow the mixture to come to a simmer, then simmer for 5 minutes.
Turn off the heat and stir in the rice noodles. Serve with the beef arranged on top.