Preheat the oven to 320°F (160°C)
Grease and line a baking tray with parchment paper.
Combine the butter and sugar and salt in a bowl or stand mixer. Mix until smooth
Add in the vanilla extract and mix.
Pour in the buttermilk and mix well, scraping down the sides of the bowl.
Stir in the cocoa powder until just combined.
Mix in the flour until a dough forms. This dough binds together quickly and has a firm, thick texture. If you feel that the dough is too sticky then just add a little flour.
Use a silicone non-stick mat or non-stick surface to roll out the dough. If you do not have a silicone mat, then place the dough between two sheets of parchment/baking paper. Use a rolling pin to roll out the dough before cutting into shapes. The rolled-out dough should be approximately 1/8 inch (3mm) thick.
Cut out the cookies using a round cutter and place them on the baking tray.
Bake the cookies for between 10 to 12 minutes until the edges are lightly crisp.