To make the pistou, put the garlic, basil and parmesan in a food processor and process until finely chopped. With the motor running, slowly add the olive oil, until you have a thick paste. Alternatively pound the ingredients using a mortar and pestle. Cover with plastic wrap and set aside.
Heat the stock in a large saucepan over medium heat, add the celery, carrot and zucchini and cook for 10 minutes.
Add the beans and stir in the vermicelli and cook for a further 10 minutes, or until the vermicelli is cooked. Season and stir through a spoonful of pistou, to taste.