Preheat the fan oven to 150 degrees Celsius (or 170 degrees Celsius static/gas 3).
Take the butter, that has been out of the fridge for about one hour, and cut into 1 cm cubes, then put it into a bowl.
To the butter, add the flour and sugar and mix well with your hands. The more you work it, the more it will start looking like big breadcrumbs.
Once it looks like big breadcrumbs, add the chocolate chips and continue working the dough until it becomes uniform.
Shape the dough like a sausage and put it in the fridge, covered in cling film, for about twenty to thirty minutes, to set.
Once set, remove it from the fridge and slice it into 25 biscuits.
Spread evenly on a baking tray that has been covered with a sheet of baking paper, ensuring there are a couple of centimeters of space between biscuits.
Bake in the oven for about 15 minutes until golden brown; depending on the oven, it will take between 13 and 17 minutes, so keep an eye on them.