Preheat a Dutch oven or 4-quart (or larger) heavy soup pot over medium-low heat until it feels warm. Add the curry paste, oil, shallot, ginger, and dry spice seasonings - coriander, turmeric, cumin, and garam masala powder. Saute over medium-low heat for 1 minute.
Add ½ cup coconut cream and keep sauteing over medium-low heat until you can see the oil starts surfacing to the top and is separated from the paste, about 3 minutes or longer. Stir often with a wooden spoon so that the paste won’t get burnt.
Add the chicken and gently stir to coat the curry paste over the drumsticks. Add the remaining coconut cream, water, fish sauce, sugar, and lime leaves, if using. Give it a stir then cover the pot and bring it to a gentle boil over medium heat, about 5 minutes. Then, lower the heat to simmer and cook for 30 minutes.
In the meantime, cook the noodles in a separate pot, following the package instructions.
Once the chicken has fallen off the bone tender, taste and start seasoning the broth further with fish sauce, sugar, and lime juice to taste. The flavor should be savory, sweet, a little spicy, and zesty sour flavor.
To serve, you can shred the chicken or serve a whole drumstick as people do in Thailand. Add the boiled noodles to individual serving bowls with chicken and a few spoonfuls of hot broth. Garnish with fried shallots, pickled chinese mustard greens, sliced shallots, and bean sprouts, if using. Serve with extra lime wedges on the side. Serve hot.
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Notes
For a thinner broth, add more water or stock.
For slow cooker: Set it on high for 4 hours or low for 6-7 hours.
Can I use boneless chicken? I don’t recommend it. You can use a combination of bone-in and skin-on chicken drumsticks or thighs along with boneless chicken. You need bones to create a flavorful broth.
Avoid letting the soup come to a boil so that the coconut milk cream won’t curdle. It won’t affect the taste but you might see white flaky bits in the broth.
For Thai soups and curry, always finish seasoning with fish sauce, sugar, and lime juice to taste.
Cook the noodles separately so they don’t interfere with the coconut chicken broth.
Must-have ingredients to make Khao soi gai: Out of all the ingredients, the must-haves are Thai red curry paste, ginger, shallot, coriander powder, turmeric powder, cumin powder, bone-in chicken, stock or water, coconut sugar, fish sauce, noodles, and lime juice.