Combine the chicken, carrots, bay leaf and a pinch of salt in a medium saucepan. Add 3 cups broth and bring to a boil; immediately reduce the heat to low, cover and cook until the chicken is just firm, about 20 minutes.
Meanwhile, heat the butter in another saucepan over medium-low heat. Add the onion, sugar and 1 teaspoon salt; cook until the onion is soft, 5 minutes. Add the curry powder and cook for 1 minute. Add the rice and the remaining 3 cups broth. Increase the heat to medium, cover and simmer until the rice falls apart, 15 to 20 minutes.
Remove the chicken from its broth; discard the skin and shred the meat into pieces. Return the shredded chicken to the same broth.
Puree the rice mixture with an immersion blender until smooth (or use a regular blender, then return to the pan). Pour in the shredded chicken and broth, stirring gently to combine; bring to a simmer. Toss in the chopped herbs and serve the soup with lemon wedges.
Photography by Antonis Achilleos
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.