• Add flour, cocoa powder and salt into a small bowl and whisk to combine.
• Add butter into another larger bowl, beat with a hand held electric beater for 1 minute. Add confectioners sugar and vanilla extract and continue beating until creamy, addional one minute.
• Add combined flour mixture and continue beating on low speed, until it looks crumbly. Make sure not to over mix.
• Transfer dough onto a work surface and gently knead to form a smooth ball. The dough should be firm, smooth and not sticky, but not crumbly or break apart when shaping.

  Pro tip: If your dough appears too dry, add a teaspoon of milk until it holds together. Conversely, if the dough seems too wet, gently mix in a small amount of additional flour or cocoa powder.
• Transfer dough onto a parchment paper and roll with the help of parchment to make a uniform log of 7 to 8 inches long.
• Wrap log in parchment and chill in the refrigerator until firm (overnight or up to 2 days).

Bake

• Pre heat oven to 340°F or 170°C. Line a large baking sheet with parchment paper.
• Remove cookie dough from refrigerator, leave at room temperature for 10 to 15 minutes. This makes it not crumble when sliced.
• Using a sharp knife, gently slice log into ¼ thick slices and place on the parchment lined baking sheet about 1 and ½ inches apart.
• Bake for 15 to 20 minutes or until done. Cookies will expand slightly, be dry and firm to the touch.
• Place baking sheet on a wire rack and cool completely.