Preheat the oven to 190 C / 170 C fan / Gas 3. Line 2 baking trays with greaseproof paper.
In a mixing bowl, cream the butter and sugars together until light and fluffy. Beat in the two eggs until thick and creamy. Sift in the flour and cocoa and beat until just mixed. Stir in the chocolate chips using a wooden spoon.
Using an ice cream scoop, scoop balls of the mixture onto the prepared baking trays, six to a tray (allowing room to spread out). Wet hands and flatten each ball slightly.
Bake on the middle shelf of the oven for 11 minutes until just golden brown. Remove from the oven and allow to cool on tray for 5 minutes before transferring to a cooling rack to cool completely before serving.