Peel and finely dice the onions. Remove the tough stems from the fennel bulb, set the green leaves aside and dice the rest. Peel and finely dice the carrot.
Put olive oil and the vegetables on a pan, put a lid on and let it cook over very low heat.
Meanwhile, peel, halve and deseed the tomatoes; dice them and add them to the remaining vegetables. Season it with 2 tsp on salt, put the lid back on and let it cook for approximately 10 minutes, stirring occasionally.
At the same time, boil the egg in salted water for 10 minutes.
Add sugar and boiling water to the vegetables. When soft, blend the vegetables and adjust the seasoning.
Peel the egg and finely dice it.
Pour the soup into serving plates and sprinkle with egg, fennel leaves and chives.
To peel the tomatoes, make a cross cut on the base and blanch it in boiling water for 1 to 2 minutes.