Peel and finely chop the onion. Peel the carrot and celery and cut into ¼-inch dice.
Put the olive oil, onion, carrot, and celery in a heavy-bottomed soup pot over medium-high heat and sauté, stirring occasionally, until the vegetables are lightly browned, about 10 minutes.
While the vegetables are browning, peel and finely chop the garlic. Finely dic