Crush half the ginger in a garlic press and reserve the juice. Slice the other half. Mix the ginger juice, 1/4 teaspoon chicken stock powder, 1/4 teaspoon sugar, cornflour and 2 tablespoons water and mix well. Mix the beef with 1 teaspoon of sugar and the rest of the stock powder. Let marinate 10 minutes.
Heat 1 tablespoon oil in a wok and sauted the sliced ginger until fragrant. Add the Chinese broccoli and stir-fry two minutes. Add 1 tablespoon water, cover with a lid and let cook for 1 minute. Remove and reserve.
Heat 1 tablespoon oil in the wok and stir-fry the beef until medium well. Add the Chinese broccoli and ginger juice mixture, stir well and serve.