Step-by-step Icebox Checkerboard Cookies
Mix flour, baking powder, vanilla sugar, powdered sugar, salt, egg and butter using a stand mixer fitted with a dough hook, then knead on a lightly floured surface to a smooth dough. Divide dough in half. Mix powdered sugar, cocoa powder and milk and knead into one half of the dough. Form each portion of dough into a ball, wrap in plastic wrap and refrigerate for about 1 hour.
To make a checkerboard pattern, form both portions of dough into ropes about 1 cm thick (approximately 1/3 inch thick). Cut each dough rope into 6 strips about the same length (figure 1).
Brush dough strips with egg white and form into a log with three layers. Form bottom layer into a pattern with chocolate, plain and chocolate dough strips. Form middle layer with plain, chocolate and plain strips. Form top layer with chocolate, plain and chocolate strips (figure 2). Repeat, forming a second log with remaining dough strips.
Thinlyl roll out remaining plain dough, brush with egg white and wrap around checkerboard-layerd dough logs (figure 3).
Refrigerate dough logs for about 4 hours. Line baking sheet with parchment paper.
Preheat oven to 180°C (approximately 350°F). Cut dough logs into slices about 1 cm thick (approximately 1/3 inch thick) (figure 4). Place cookies on prepared baking sheet and bake for 20-25 minutes. Let cookies cool before serving.