200g unsalted butter
300g caster sugar
2 eggs, beaten
250g white flour
2 tsp baking soda
1/4 tsp salt
70g unsweetened cocoa powder
200g chocolate chips

Beat the butter and sugar until pale and fluffy.
Add the beaten eggs gradually while beating.
Sift together the flour, baking soda, salt, cocoa powder then fold into the butter/sugar mixture using a large metal spoon.
Fold in the chocolate chips.
Chill the mixture for 1 hour.
Preheat the oven to 160°C.
Line the baking sheets with parchment paper.
Divide the cookie mixture into equal-sized balls. Bake in the centre of the preheated oven for 15-20 minutes.
Let stand on the baking sheet for one minute then remove with a spatula to a wire rack to cool completely. Store in an airtight container.