Clean the clams, cook them over high heat in 50 cl of water and remove them as soon as they open. Peel and reserve them. Filter the cooking juices to remove the sand.
Peel and finely chop the onions and garlic. Clean and cut the leek into fine julienne. Scald the tomatoes for 2 minutes, then peel, seed and chop them. Peel and dice the potatoes.
Brown the onion with the oil in a saucepan, without letting it brown. Add the garlic, tomatoes and potatoes. Moisten with the wine and the cooking juice of the clams, then add the thyme, the bay leaf, the saffron (1 dose) and the shellfish stock. Season with salt and cayenne. Let simmer for about 30 minutes. Add the clams 5 minutes before the end.
Make the rouille:degerminate and pound 1 garlic clove into a fine ointment in a mortar with a pinch of salt and cayenne. Add a dose of saffron and the egg, then gradually incorporate the oil as if to make mayonnaise. Reserve at room temperature.
At the same time, blanch the leek julienne for 5 minutes in boiling salted water, then drain and immediately pour it into a basin of ice water to set the color.
Remove the thyme and bay leaf from the soup. Take 12 clams for the decoration, then put the velouté in the blender. Add the leeks and continue cooking for another 5 minutes.
Adjust the seasoning of the velouté, then pour in the liquid cream and the whole clams. Sprinkle with chopped chives and serve at the table immediately, with the rouille on the side in a sauce boat.
