Make the Vanilla dough: Sift flour, baking powder and salt. Set aside.

In the bowl of a stand mixer fitted with paddle attachment or in a large mixing bowl with hand mixer, cream butter and sugar until light and fluffy.

Add egg and vanilla extract, beat until combined.

Slowly add the dry ingredients and beat just until combined.

Divide the dough into half. Pat the dough into a disk and wrap one half in platic wrap and refrigerate for about 30 minutes.

Make the chocolate dough: Add cocoa powder to melted semi sweet chocolate and mix until well combined.

Add this chocolate to half of the dough and mix until chocolate is incorporated. Pat into a disk and refregirate to chill for about 30 minutes.

Making Pinwheel cookies: Once both the doughs are chilled, place each disk in between 2 sheets of wax or parchment paper. Roll out both the doughs into approximately 12" squares.

Remove the wax paper from the top of both the rolled out squares. Now flip the chocolate square and place it right over the top of vanilla square. Roll lightly on the top so both the doughs stick to each other.

Start rolling the dough into a tight log using the wax paper as a guide. Wrap the log in plastic wrap and refrigerate for at least 2 hours.

Preheat oven to 350°F. Line Baking sheet with parchment paper or silicon mat.

Trim the edges off and cut the dough log crosswise into ¼" slices. Place them on the baking sheet 1" apart.

Bake for 10-14 minutes or until the cookies are slowly starting to firm up.

Cool the cookies on the baking sheets for 3-4 minutes before removing them onto cooling racks. Store them in air tight container for at least 1 week.