Put the Onion, Carrot and Celery in the food processor and blend until it’s a finely diced (or chop them with a knife)
Add the olive oil to a large saucepan on a medium heat
Add the Onion, Carrot and Celery mixture to the pan and sauté for 5 mins
Whilst, cooking, chop the garlic
Add the chopped garlic to the pan and continue to cook a few a few mins