Heat the oil in a large saucepan over low heat. Add the garlic, and cook for 5 minutes. Add 2 of the basil leaves and stir for 1 minute. Add the tomatoes with their juice and the 2 remaining basil leaves. Turn the heat to high. Bring the sauce to a boil, turn the heat to low, season with salt and pepper, and let it bubble away on low heat for 45 minutes, stirring occasionally and crushing the tomatoes with a wooden spoon. Cool and refrigerate.