Preheat the oven to 160°C Fan/180°C (350°F) and line a baking sheet with parchment paper.
To a bowl, add softened butter, white granulated sugar and light brown sugar and whisk them together until smooth.
Add in the egg and vanilla extract and mix in.
Whisk in the plain flour, cocoa powder, baking soda and salt and mix together until it forms a cookie dough.
Add chocolate chunks and mix into the dough.
Roll the cookie dough into small balls around 1 inch in size, gently flatten and place onto a baking tray lined with parchment paper.
Place the cookies into the pre-heated oven for 15 minutes.
Once they come out of the oven. allow them to cool before tucking in; they should be chewy and delicious!
