1. In a large bowl, cream together the butter and sugar until light and fluffy. This will take about 2 minutes.

2. In a separate bowl, whisk together the flour, cocoa powder, and salt.

3. Gradually add the dry ingredients to the butter mixture, mixing until a dough forms.

4. Roll out the dough on a lightly floured surface to about 1/4 inch thick.

5. Use a heart-shaped cookie cutter to cut out cookies, then place them on a baking sheet lined with parchment paper.

6. Chill the cookies in the refrigerator for at least 30 minutes before baking.

7. Preheat the oven to 350°F (175°C) and bake the cookies for 12-15 minutes, or until set.

8. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.