1. Prepare the sauce by mixing together the potato flour, mushroom water, oyster sauce, and soy sauce. Heat a wok and add 2 tablespoons oil and swirl around. Add the garlic, letting it sizzle and then add the white part of the onion and then the Chinese mushrooms. Stir for about 30 seconds and pour in the potato flour mixture. Lower the heat and continue to stir until the sauce thickens. Remove from heat.

2. Heat 1 tablespoon nut or corn oil in a wok over a high heat until it starts to smoke. Add the ginger and when it starts to sizzle, add the cabbage and green pepper. Toss for about 30 seconds. Season with a little salt, lower the heat and continue to cook, covered for a further 2 minutes. Remove and put into an earthenware pot or saucepan.

3. Now half fill the wok with oil, heat to 200 degrees and lower the bean curd into the oil, one piece at a time, and deep-fry for 4 minutes or until golden brown, turning over from time to time. Remove with a large strainer and drain on paper towels.

4. Lay the bean curd on the cabbage in the pot and add the green part of the onion. Heat the sauce and pour this over the bean curd. Heat the pot for 2 minutes and serve.