In a medium bowl sift in the flour, baking powder, cocoa and salt.
Beat the butter and sugar until creamy, approximately 2 minutes. Add the egg, milk and vanilla and beat 1 minute. Add the dry ingredients half at a time, and combine on low speed #1-2, beat just to combine, do not over mix. The dough quite tacky, if too wet then add a bit more flour.
Place the dough between two pieces of parchment paper and pat into an oval shape. Place on a baking sheet and refrigerate for 1-2 hours.
Leave the dough in the parchment paper and roll it to ¼ inch / 1.2cm thick. Cut out with your favourite cookie cutters (2-3 inches/5-7½ cm) and place on a parchment paper lined baking sheet or two. Chill while the oven is pre-heating.
Pre-heat the oven to 350F/180C.
Bake for approximately 9-11 minutes. Let cool 10 minutes on the pan then move to a wire rack to cool completely. Dust with powdered sugar/icing sugar or dip or drizzle with melted chocolate if desired. Enjoy!
Notes
Chocolate cookie dough is naturally tacky, but if it feels too soft to roll, chill it longer or add a small spoonful of flour until it firms up or if it is too dry add a bit more milk to bring it together.
How to store the Chocolate sugar cookies?
Keep them in an airtight container at room temperature. They stay soft for several days and undecorated chocolate sugar cookies can be frozen for up to 3 months if you want to make them ahead. To freeze, wrap the dough well and freeze it for up to two months. Let it thaw in the refrigerator, then roll and cut as usual. You can also freeze unbaked cut-out cookies by flash freezing on a parchment lined baking sheet then storing in a freezer safe bag. Thaw for 15 minutes at room temperature before baking.