Pour 2 tbsp of oil in a Wok or dish (you may use the same oil in which the Manchurian balls were fried)
Once the oil is hot, add the chopped garlic, ginger, green chillies and spring onions (only half of the amount) and saute for about a minute until fragrant
Now add the Chicken/Veg Stock cube, Soy Sauce, Chilli Sauce, Tomato Sauce and Vinegar to the mixture and saute it for about a minute
Add the Salt, Black Pepper Powder, Salt and Paprika and stir well (check the Salt level before adding salt as Soy Sauce and Chicken/Veg Stock cubes both have salt content in them)
Add 1 cup of Water and let it come to a boil
Now take the other 1 cup of water and add the cornflour to it and mix well
Pour the cornflour mixture to the gravy and let it simmer for about 4-5 minutes on low flame, stirring from time to time until the gravy becomes thick in texture.
You may add more cornflour if you like the gravy to be more thick. Do keep in mind that once the gravy cools down it will become thicker.
Now add the fried Manchurian balls to the gravy and let it simmer for about 4-5 minutes on slow flame
Dish it out in a bowl and garnish with remaining of the spring onions
Serve fresh with fried rice, noodles or steamed rice