Fry clams in a pan with a lid to help them open. Keep some cooking liquid and shell.
Chop the carrot, celery and leek and sauté in a pan. Add diced tomatoes and cook for 5 minutes with a little cooking liquid of the clams. Add salt and pepper and the clams.
Fry leek roots in a saucepan in plenty of seed oil.
Cook Clam in boiling salted water for 2 minutes, stirring gently. Drain using a skimmer and empty each piece of all cooking water.