Preheat your oven to 150°C (300°F) for traditional ovens or 300°F for fan ovens.

In a large mixing bowl, cream together softened butter, powdered sugar, fine salt, and optional vanilla extract using an electric mixer for about 3 minutes.

Gradually add half of the all-purpose flour and Dutch cocoa powder to the creamed mixture until a dough starts to form, then add remaining flour and cocoa.

Shape your biscuits by either pressing the dough into a baking tray, rolling into a log, or cutting with cookie cutters.

Bake shaped biscuits for 20 minutes, then allow to cool completely in the tin or on the baking trays.

For optional coating, melt dark chocolate with vegetable oil and dip cooled biscuits, then set on a parchment-lined tray.