In a mixing bowl, cream together the butter, powdered sugar, salt, and vanilla extract for about 3 minutes until pale and fluffy. Gradually add in half of the sifted flour and cocoa powder, mixing until combined, then repeat with the remaining dry ingredients until a soft dough forms.

If your dough is too soft, cover it in plastic wrap and refrigerate for 30 minutes to firm it up.

Preheat your oven to 150°C (300°F) for fan-off or 130°C (265°F) for fan-on.

For slice and bake, press the dough into a lined baking tin, chill for 1-2 hours, or roll out for cookie shapes.

Transfer shaped biscuits onto an ungreased baking sheet and bake for about 20 minutes until edges are slightly golden.

To add a chocolate coating, melt the dark chocolate and stir in vegetable oil until smooth.

Dip each cooled biscuit into the melted chocolate, allowing excess to drip off.