On a medium flame, heat the oil in a medium stockpot. Add the chicken thighs and sauté lightly for eight minutes, turning once. Add the onion, carrot, turmeric, black limes, parsley, peppercorns and a teaspoon of salt. Pour over 1.5 litres of water, bring to a gentle simmer, cover and cook for 40 minutes. Use a slotted spoon to lift all the chicken and vegetables out of the broth (save the chicken for use in a salad or sandwich filling). Return the limes to the liquid and set the pot aside.
Put all the ingredients for the dumplings in a large bowl with a teaspoon of salt. Mix well and, with wet hands, shape into 16 round, 30-35g dumplings.
Bring the broth to a gentle boil and add the cannellini beans. Carefully lower the dumplings into the broth, cover with a lid and simmer on a low heat for 30 minutes. The dumplings will expand in the liquid. Remove the lid and simmer for another 20 minutes, until the soup has concentrated in both consistency and flavour. (Add water as necessary, or reduce the liquid for longer.) Serve in bowls and top with a squeeze of lime and some coriander.