01 -
In a mixing bowl, cream together the butter and sugar until light and fluffy, about 3 to 5 minutes. Blend in the egg and vanilla extract. In a separate bowl, whisk flour, baking powder, and salt. Gradually incorporate dry ingredients into the butter mixture, mixing until a smooth dough forms.
02 -
Repeat the same method for the chocolate dough: Cream butter and sugar until light and fluffy. Add egg and vanilla. In a separate bowl, combine flour, cocoa powder, baking powder, and salt. Integrate dry ingredients into wet ingredients until a uniform chocolate dough is achieved.
03 -
Divide each dough in half. Shape each portion into a rectangle, wrap tightly in plastic, and refrigerate for a minimum of 1 hour to firm the dough.
04 -
On a lightly floured surface, roll out each dough portion into a 1/4-inch thick rectangle of equal size. Alternately layer vanilla and chocolate dough, gently pressing after each layer to eliminate air pockets. Use a rolling pin to smooth the top. Wrap the layered block and chill for at least 30 minutes.
05 -
Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper. Slice the layered dough block into 1/4-inch thick cookies using a sharp knife. Arrange cookies on the prepared baking sheet, leaving space between each. Bake for 10 to 12 minutes, until the edges are just set. Allow cookies to cool completely on the baking sheet.