If you want chocolate chips inside, mix them in the muffin mixture. Also, they may take a shorter amount of time to bake, so keep an eye on them.
Very easy and quick to make. I used butter in stead of oil. At 135g light brown sugar it was not very sweet at all, perhaps a little more for most tastes. My young boys loved it, light and fluffy, absolutely fine for them. - 11 May 2014