Bring a medium pot of salted water to boil. Meanwhile, remove fava beans from the shell. Blanch the beans in boiling water for about 1 minute and then drain and shock in ice water to coll.Remove the beans from the tougher outer pod. (The should pop out easily after being blanched). Cut the leek in half lengthwise leaving root end intact and rinse the layers thoroughly to remove sand. Cut the tough green parts off leaving only light green and white. Thinly slice each leek half. Heat olive oil in a heavy bottom skillet over medium heat. Saute the sliced leeks for about 4 minutes until soft, do not brown. Add the garlic and saute for another minute, until softened. Make sure not to brown the leek and garlic, keeping the heat on medium and adding extra oil if needed. Add the shelled beans to the pan and saute for 4 minutes. Season with salt and pepper and serve.