To the same pan, add onion petals, ginger, green chillies and saute for 1-2 minutes. Add spring onions and saute on low for a few seconds till fragrant. Add lime leaves, lemon grass roots and greens, saute for a few seconds, add coconut milk, water, salt and cook for 10 minutes till the broth gets the flavour from the aromatics. Take off the heat, add lemon juice and mix well.
¾ cup onion petals, 1 ½ inch ginger, 3 green chillies, ¼ cup + 2 tablespoons spring onion whites, 4 kafir lime leaves, 3 lemon grass roots, 3 lemon grass greens, 4 ½ cups water, 1 ½ cups coconut milk, ¾ teaspoon salt, 1 ½ teaspoons lemon juice