In a large cooking pot (3 qt), place the chicken drumsticks, roughly chopped onion, ginger, garlic pods, cilantro stems and scallion white parts. Also add the bay leaf and black peppercorns.
Sprinkle salt and pour water into the pot to cover all the ingredients. Cover the pot with a tight fitting lid and place on low medium stove.
Once the water comes to a boil, skim the top if needed, cover again, reduce the stove to low flame and let the soup simmer for 45-50 minutes. This long cooking extracts sufficient flavor, fat and gelatin from the chicken.
Using tongs remove the cooked chicken and place on a plate to cool down. Separate the chicken meat from the bones. Shred the meat and keep aside.
Strain the chicken broth into a large bowl using a mesh strainer. Press down the softened vegetavles a few times to extract every flavor into the broth. Pour it back into the cooking pot and return the pot to the low stove.
Add the sriracha,soy sauce and ground black pepper. Once the soup is simmering again, add back the chicken. Squeeze lemon juice.
Add the vegetables towards the end and let simmer for 1-2 minutes. This short cooking makes sure that the vegetables don't soften too much.
Mix in the corn starch slurry. Cook the soup for 2-3 minutes and then switch off the stove.
Immediately pour into serving bowls and top with generous scatter of chopped fresh cilantro and green parts of scallions. Serve!
Storing - The soup is best served immediately. If you want to serve it later, don't add the vegetables while cooking it else they soften too much. Add them when you warm up the soup. You can store this soup refrigerated for 3-4 days.