Heat the oil in a large pan and gently fry the garlic slivers until light brown. Add a few of the basil leaves and then the tomatoes. Stir and cook gently for 30-40 minutes, until reduced to a thick sauce. Season with salt and pepper and add the remaining basil.
Cook the penne in a generous amount of boiling salted water, drain thoroughly and return to the saucepan with the butter. When