Preheat your oven to 200°C (180°C Fan, gas mark 6) and line a baking tray with parchment paper.
In a large mixing bowl, whisk together the butter, caster sugar and light brown sugar until the mixture is pale and creamy.
85 g Brown Sugar, 85 g Caster Sugar, 125 g Unsalted Butter
Add the egg and vanilla extract to the bowl and mix again until combined.
1 Large Egg, 1 tsp Vanilla Extract
Add the remaining dry ingredients (apart from the chocolate) to the mixing bowl and whisk again until a cookie dough has formed. Then add the white chocolate chunks and gently mix it into the cookie dough.
185 g Plain Flour, 1 tsp Baking Powder, 1 tsp Bicarbonate Of Soda, 40 g Cocoa Powder, ½ tsp Salt, 200 g White Chocolate
Scoop a heaped tablespoon amount of dough and roll each portion into a ball, placing them on the lined baking tray evenly apart (they will spread out whilst baking).
Bake the double chocolate cookies in the oven for 8 minutes (or 10 minutes for a crisper texture). Leave the cookies to cool down completely on the baking tray before transferring. Enjoy!