In a large pot, set the stove to medium heat and add 1-2 tablespoons of oil into it and wait for it to get hot
Add in the lemongrass, lime leaves, garlic, and ginger and the khao soi curry paste and toast it for 1-2 minutes. (The curry paste may stick to the bottom of the pan, that's perfectly okay!)
Once the spices are aromatic and toasted, add in the coconut cream and coconut milk. Using a spatula, scrape off any curry paste that has stuck to the bottom of the pan, with the coconut milk. Cook it for about 1-2 minutes.
Add the chicken stock, fish sauce and sugar and stir until everything is combined, and wait for the soup to come to a boil
Once the soup starts boiling, turn the heat down to low and put a lid on the pot. Let it simmer for 30 minutes
After 30 minutes, fish out the spices (lemongrass, ginger, garlic and lime leaves) and do a taste test and adjust it to your liking. (If it is not salty enough - add a little bit more fish sauce, if you like your soups a bit more sweet - add a bit more sugar in)
(Optional) If you adding chicken drums to the recipe, add it in now and cook it for another 30 minutes with the lid on.
(Optional) I personally like my curry soup to have a soupy consistency but if you prefer a thicker consistency in the soup, continue to simmer the soup (with the lid removed) for an additional 10-15 minutes to reduce the liquid.
Keep it on the stove on low heat with the lid on to keep it hot while you prep the noodles and are ready to serve it.