Heat the olive oil in a large pot or Dutch oven over medium heat. Add the leek, carrot and celery and season with salt and pepper. Cook for about 5 to 6 minutes, stirring often, until the vegetables start to soften.
2 tablespoons olive oil
1 medium leek
1 medium carrot
2 celery stalk
½ teaspoon salt
¼ teaspoon freshly ground black pepper