Heat 2 tbsp of oil in a broad non-stick pan, add the idli and sauté on a medium flame for 3 to 4 minutes or till it turns light brown in colour. Keep aside.
Heat the remaining 1½ tbsp oil in a broad non-stick pan, add the ginger, garlic and green chillies and sauté on a medium flame for a few seconds.
Add the onions and sauté on a medium flame for 1 minute.
Add the capsicum and sauté on a medium flame for 1 more minute.
Add the tomato ketchup, sugar, vinegar, soya sauce, red chilli sauce and salt mix well and cook on a medium flame for 1 minute, while stirring continuously.
Add the sautéed idlis and spring onions, mix gently and cook on a medium flame for 1 to 2 minutes, while tossing occasionally.
Serve immediately garnished with spring onions.