Roughly tear half the basil leaves and finely chop all the stalks. Reserve the remaining leaves to serve. Bring the stock to the boil in a small saucepan.
Heat the olive oil in the insert pan of a slow cooker or a frying pan over medium–low heat. Add the garlic, tomatoes, torn basil leaves and chopped stalks and cook, stirring occasionally, for 5 minutes, or until softened and the tomat