Drain the tofu and pat dry with kitchen paper before cutting it into 20 equal-sized cubes. Set aside. Pour enough oil for deep-frying the tofu into a wok, and heat it to 190°C (375°F), or until a cube of bread dropped into the oil turns golden in 20 seconds. Add half the tofu and deep-fry until puffy and golden, then remove using a slotted spoon and drain on kitchen paper. Sir-fry the remaining tofu in the same way. Set aside.
Pour off all but 2 tablespoons of the oil and place the wok over a high heat. Add the ginger and garlic and give it a quick stir, then add the mushrooms and sugar snaps.
Stir-fry for 2 minutes, then return the tofu to the pan and toss in the oyster sauce and rice wine. Cook, stirring, for a further 1–2 minutes until the tofu is well coated and has soaked up some of the sauce. Remove from the heat and serve with a scattering of sliced chilli.