Heat the oil and the saucepan over medium heat. Add the ground turkey and sauté until it is all browned.
Add the garlic, onion, carrot, celery, and tomato paste and cook until the onions are translucent, about 3-4 minutes. Stir frequently to make sure the onions don’t burn to the pan.
Add the tomatoes and half of the basil leaves and cook until the sauce starts to simmer. Add the salt and pepper. Turn the heat to low, and reduce the sauce for another 30 minutes. Reducing makes the sauce thicker by cooking out the extra water. Turn off the heat.