Hix the soy sauce with 2 tbsp water and the cornflour, and keep to one side. In a wok, heat the oils together and stir-fry the mushrooms with salt and pepper until they’re seared a little. Throw in the garlic, ginger and chillies and stir through, then add the vegetables and beansprouts. Stir-fry over a fierce heat for about 1 minute, adding a dash more seasoning. Pour in around 150ml water, bubble up for about 30 seconds, then stir in the cornflour mixture and the oyster sauce and bubble up to make a good gloopy sauce. Serve piled on to plates or in bowls, and sprinkle each serving with toasted sesame seeds.