1 leek, white and light green parts only, thinly sliced [be sure to cut it vertically first and to wash the layers under running water, or you might get sand in your soup]
2 carrots, cut into 1/4-inch dice
2 celery stalks, cut into 1/4-inch dice
2 to 3 garlic cloves, thinly sliced, plus 1 whole garlic clove