2) In a medium bowl, combine the flour, sugar, baking powder, bicarbonate of soda and salt. Cut in the vegetable fat with a fork until it looks like fine breadcrumbs. Add the buttermilk, a little at a time, stirring constantly until well mixed.
3) Turn the dough out onto a lightly floured surface. Knead lightly two or three times. Roll out the dough with a floured rolling pin to 13mm thickness. Cut dough into circles with a 5cm cutter.
4) Place the biscuits in a greased roasting tray. Gently press down the top of the biscuits. Brush the biscuits with half the melted butter and bake for 14 minutes or until golden brown.
5) Meanwhile, make the chocolate gravy. Heat the butter in a saucepan set over a low heat. Mix in sugar, flour and cocoa. Slowly pour 240ml milk into the pan, whisking well to remove lumps. Whisk in remaining milk, stirring constantly, until the mixture is thick, being careful not to let the mixture burn on the bottom of the pan.
6) Brush the hot biscuits with the remaining butter.
7) Split the biscuits in half, ladle the chocolate gravy over and serve at once.