Preheat your oven to 180ºc/160ºc Fan/375F and line two-four baking trays with parchment paper. Mine are quite large trays (40cm) to make sure the cookies don't touch!
Mix together the butter and both sugars until light and fluffy and thoroughly combined! Using an electric mixer is far easier for this because it gets very fluffy and perfect!
Mix in the vanilla and the egg until thoroughly combined, then mix in the cocoa powder, flour, bicarbonate of soda, baking powder and salt until a thick paste/cookie dough is formed.
Fold in the chocolate chips, and spoon the mixture onto the trays and make sure they are suitable spread out so they stay separate! (I usually fit 6-8 on each tray to be safe) I also use a 5cm cookie dropper/ice cream scoop to make them identical sizes.
Bake in the oven for 10-12 minutes until spread out perfectly crinkly. A minute or so less will be gooey, a minute or two more will be beautiful and crunchy.
Once baked, remove from the oven and gobble them all up - don't burn yourself on the chocolate!
Notes
Recipe updated August 2019
Original recipe
Everything is the same, apart from the original used to use 175g self raising flour instead of the 225g plain. I also used slightly less chocolate chips. Method and everything else is the same.