1. Tip 200g flour into a large mixing bowl and add a good pinch of salt. Pour in 325ml cold water and whisk together well till smooth. Use some kitchen paper to rub a small amount of oil onto the surface of a non-stick frying pan. Warm to a low-medium heat and brush some of the pancake batter onto the pan, to form a thin pancake. Once enough batter is in the pan, turn the heat up slightly until the pancake is set, but not crisp. Flip the pancake over and cook for a further 10 secs, then transfer to a wire rack to cool. Repeat with the rest of the pancake batter to make 4-6 pancakes in total. Set aside.
2. Mix 2 tbsp cornflour with 2 tbsp cold water in a small bowl. Pop the bowl to one side. Remove the core from ¼ green cabbage and thinly slice the leaves. Peel and chop the carrots into matchsticks. Trim the roots and any dry ends off the spring onions, then thinly slice them. Thinly slice the mushrooms, brushing off any dirt.
3. Peel and grate the garlic and ginger into a separate small bowl. Add 1 tsp sesame oil, 1 tbsp shaoxing wine, 1 tsp sugar and 2 tbsp tamari and stir together well. Set aside.
4. Pour 1 tbsp oil into a large frying pan or wok and warm to a medium-high heat. Crumble the pork mince into the hot pan and add a pinch of salt and pepper. Fry the mince, stirring occasionally, for 5-6 mins, till browned and starting to go crispy. Slide the cabbage, carrots, mushrooms and spring onions into the pan. Pour the garlic and ginger mix into the pan and stir well. Continue to cook for 3-4 mins, stirring, till the veg are softened. Pour in most of the cornflour mixture (save a little for later) and stir well till no standing liquid remains in the pan. Scoop the contents of the pan into a bowl and allow to cool.
5. Arrage a pancake on a flat surface and add 2 tbsp of the filling mixture to the middle of the pancake. Fold the sides of the pancake in, then roll into spring rolls. Just before you get to the end of the pancake, brush a little of the remaining cornflour onto the edge, then press to seal. Repeat with the rest of the pancakes.
6. Pour 1½ ltrs sunflower oil into a large, heavy pan or deep fat fryer and warm to 180°C. When the oil is hot, carefully add some of the spring rolls into the pan (making sure not to crowd the pan). Fry the spring rolls for 5-6 mins, using a spoon to turn occasionally, till the pancakes are crisp and golden.
7. Transfer the cooked spring rolls to a plate lined with kitchen paper and allow to drain. Repeat till you have cooked all of the spring rolls. Serve straight away with your favourite dipping sauce on the side.