In a bowl, whisk the butter and sugar until they achieve a smooth texture.
Incorporate the egg and vanilla essence, blending well.
In a separate bowl, sieve the flour, baking soda, and salt. Slowly integrate this dry blend into the creamy butter mix.
After blending, split the dough into two even sections. To one part, mix in the cocoa powder until evenly colored.
Cover both dough sections and let them rest in the refrigerator for about 30 minutes.
Roll out both doughs separately to ¼ inch thickness.
Place the chocolate dough over the vanilla one and gently roll them together. Slice into pinwheel shapes using a cookie cutter.
Position the Maurice Lenell Pinwheel Cookies on a tray layered with baking parchment.
Preheat the oven to 375°F (190°C) and let the cookies bake for about 8-10 minutes, or until they take on a light golden hue.
After baking, let the cookies rest on the tray for a few moments before moving them to a wire rack to cool further.