For the soup, heat the butter in a large pan until foaming, then fry the onion and garlic together with the curry powder for 2-3 minutes, or until softened. Add the sweetcorn and fry for a further minute, then pour in the chicken stock and bring to a simmer. Cook for 2-3 minutes.
Add the crabmeat to the pan and bring to the boil. Take off the heat immediately, then transfer to a food processor and blend to a smooth purée.
Return the soup to a clean pan set over a medium-low heat. Stir in the cream, lemon and lime juice, then season with salt and freshly ground black pepper. Keep warm.
For the beignets, place the water and butter into a pan and bring to the boil for one minute. Remove from the heat and stir in the flour immediately, beating continuously with a wooden spoon until the mixture is smooth and comes away easily from the side of the pan.
Return the pan to the heat for 1-2 minutes to heat through. Remove from the heat and add the eggs one at a time, beating well between each addition. Stir in the sweetcorn, coriander and lime juice, mixing until well combined. Season with salt and freshly ground black pepper.
Half-fill a deep, heavy-based pan with vegetable oil and heat to 180C/355F (check using a digital thermometer. CAUTION: hot oil can be dangerous. Do not leave unattended.) Drop teaspoonfuls of the beignet batter in batches into the hot oil and fry for 2-3 minutes, or until golden-brown and crisp. Remove with a slotted spoon and drain on kitchen paper. Repeat with the remaining beignet mixture.
To serve, ladle the soup into serving bowls and place a few beignets on top. Garnish with a few coriander leaves.