Scoop the thick coconut cream from the top of just one of the cans into a large stockpot set over a medium-high heat. Melt the cream, add the curry paste and stir for a few minutes until they begin to sizzle. Add the cilantro roots and chicken and saut? until the chicken is cooked through, about 5 minutes. Add the coconut juice from the first can and all the contents of the second can along with the chicken broth, carrot, lemon grass, fish sauce, grated ginger and lime zest and juice. Simmer for 20 minutes or so. In a separate pot, bring a potful of water to a boil and add the rice noodles, remove from heat and let stand until the noodles soften, about 5 minutes. Rice noodles don?t need to simmer like pasta to cook; they simply need to rehydrate in the hot liquid. Drain liquid and set aside in a separate bowl and mix in some vegetable oil to keep noodels from sticking. Remove the lemon grass stalks from the broth and add the mushrooms. Taste and season with a touch more salt (or soy sauce) as needed. Let soup simmer another 3 minutes until the mushrooms slightly soften. Ladle noodles into the bottom of large serving bowls and ladle the soup over the noodles. Garnish as desired with the green onions and cilantro leaves. Serves 4 Variations: You can also substitute beef or shrimp for the chicken.