Assemble: all the ingredients.
In a bowl add enough water to make a cornflour paste. Make sure there are no lumps in this paste. If some lumps are formed then strain it through a strainer. Set it aside.
In a pan heat olive oil. Add ginger and garlic paste and saute for few seconds. Add green and red capsicum and saute for 2 minutes.
Mix in 1/4 cup of spring onions and rest of the ingredients one by one leaving out cornflour paste. Save 1/4 cup of spring onions - use that to top the manchurian gravy.
Pour in vinegar, tomato ketchup, soy sauce and mix.
Add 3 tablespoon water and mix. Stir and pour in cornflour paste. Keep stirring, make sure no lumps are formed. With the above mentioned proportions, manchurian gravy will become thick once cornflour is added, add extra 1/4 -1/2 cup of water to make it reach the consistency you like. I prefer mine to be saucy so I added 1/2 cup of water.
Add manchurian balls and simmer it for a while. Cover and let the manchurian balls soak in all the flavor.
Before serving garnish manchurian with leftover 1/4 cup spring onions.
Serve hot with warm rice or noodles of your choice.