When I add basil to a dish should I tear or cut basil leaves? Does it matter?
Tearing is for artistic effect
Some people will claim tearing does not damage the cell of the plant as much as cutting, a simple look under a basic microscope will show you otherwise. Not sure how this would affect basil in particular. What dish are you preparing?
If you want more basil flavour and smell, cut it more finely, or bruise it (back of knife or rolling pin) to release more oils just before serving
If you choose to cut basil with a knife, gently rub olive oil all over it before you cut it, this will prevent the leaves from darkening , particularly if you are using it in a salad.