In a medium mixing bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.

In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl using a handheld mixer, cream together the butter and sugar until smooth, about 2 minutes.

Add the egg and mix again until smooth.

Add the milk and vanilla and mix again until smooth.

Add the dry ingredients into the wet ingredients bowl and mix until just combined.

Chill the dough for at least 2 hours or up to 2 days.

When ready to bake the cookies, line 2 baking sheets with parchment paper and preheat the oven to 350 degrees F.

Pour some decorator’s sugar in a small bowl. Roll the dough into 1 ½ Tablespoon balls, using a cookie scoop if you have that size. Dip one side of the dough ball into the sugar. Place the cookie, sugar side up on your prepared baking sheet until the sheet is full, leaving about 2 inches in between cookies.

Bake for about 8-11 minutes or until the top is puffed up and the tops look mostly set.

Remove from oven and let them cool on the cookie sheet for 8-10 minutes before removing to a wire rack to finish cooling.