Cream the butter and sugar and beat for 8-10 minutes until creamy and pale.
Add the egg and vanilla and beat for another 2-3 minutes or until well combined.
Add the flour and mix till a smooth dough forms. Do not over mix. Over mixing results in tough cookies.
Remove ⅔ of the dough. Set aside. Add the cocoa to the mixer and beat until well combined.
Roll each dough portion out between 2 sheets of parchment paper to 3mm thick and refrigerate for 30 minutes or until firm.
Preheat oven to 325F. Using a 7cm round cookie cutter (I used a fluted cutter since I do not own round cutters). Cut 8 rounds from the vanilla dough. Using a 4.5 cm star shaped cutter, cut stars from the cocoa dough and place on top of vanilla dough. I did some reverse ones with chocolate rounds and vanilla stars, because that's how I roll.
Place the cookies on a parchment lined baking tray and bake for 12-13 minutes or until lightly golden.
Allow to cool on wire racks before serving.
Recipe by The Novice Housewife at https://novicehousewife.com/2014/01/02/vanilla-and-chocolate-star-cookies/