Heat oil in a wok/heavy bottomed pan, add ginger, garlic, and finely chopped green chillies, saute on medium-high heat until aromatic.
In go all the veggies next except for the scallions, stir-fry for 1-2 minutes.
Next, add chopped scallions, saute for 30 seconds
Mix well and add vegetable stock or water and the soy sauce, green chili sauce, sugar & pepper powder. Bring to a boil, cook for another 2-3 minutes. Do not overcook the veggies, they should still retain a bite. Stir the cornflour slurry again, as it has a tendency to settle down, and add to the soup, keep stirring until the soup thickens.
Add the vinegar, mix well, check for seasonings, add salt if required. Serve the soup immediately, garnish with finely chopped scallion greens along with chilli vinegar, soy sauce and chilli sauce on the side.