Preheat the oven to 180ºc / Gas 4 and line 2 baking trays with grease proof paper.
Beat the margarine and sugar together with an electric whisk until light and fluffy.
With a wooden spoon, sift in half the flour and cocoa powder and combine, add the remaining flour and cocoa powder and mix together to form a soft dough. You may find using your hands is better. Tip: You might think the mixture is dry, it's absolutely fine, they will turn into delicious cookies.
Divide the dough into 16 small round balls, spacing well apart on the baking tray. Dip a fork in water and flatten each ball to give the biscuits a ridged surface.
Bake in the oven for 15-18mins. Leave the biscuits on baking sheets until firm to touch, then serve with a cuppa tea or a glass of chilled cold milk.