Put the butter and icing sugar in the bowl of a mixer with a paddle attachment and beat them on medium speed for about 3 minutes or until the mixture is very smooth.

Then reduce the speed to low and add the salt, flour, and cocoa powder mixing only until just incorporated.

Flatten the dough into a disk, wrap it in plastic wrap, and chill the dough in the fridge for at least 1 hour.

Roll out the dough into a 0.5 cm – ¼ inch thick sheet. Cut into hearts using a lightly floured cookie cutter.

Place the cookies on a tray lined with baking paper and place in the fridge for 15 minutes (this will help the cookies retain their shape when baked).

Bake in a preheated oven at 170°C – 340°F on the middle rack for 13 to 15 minutes.

Let them cool down for 5 minutes, then transfer them to a wire rack to cool completely.