Start with the vanilla layer. In a mixing bowl, combine the soft butter with powdered sugar, starch, and flour. Use your hands or a mixer to blend them until the mixture resembles a crumbly dough.

Add one large egg and the vanilla extract to the dough. Knead it gently until everything is well combined. If the dough feels too soft, don’t hesitate to add a little more flour until you achieve a workable consistency.

Wrap the dough in cling film and refrigerate for about an hour. This step is crucial as it helps the cookies maintain their shape during baking.

While the vanilla dough chills, prepare the cocoa layer. Mix the soft butter with the powdered sugar, starch, flour, and black cocoa in another bowl until you have a crumbly dough similar to the vanilla layer.

Incorporate the other large egg into the cocoa mixture and knead slightly. Again, if it’s too soft, add more flour as needed.

Once ready, wrap the cocoa dough in cling film and refrigerate for the same duration as the vanilla dough.

After both doughs are chilled, remove the vanilla dough from the fridge. Roll it out on a lightly floured surface into a rectangular sheet approximately 0.3cm thick.

Repeat the rolling process with the cocoa dough, aiming for the same thickness as the vanilla layer.

Place the cocoa dough atop the vanilla dough carefully, ensuring an even coverage. Gently roll them together into a tight log.

Wrap the log in cling film and freeze for about 10 to 15 minutes. This will make slicing much easier.

Preheat your oven to medium heat (around 180°C or 350°F). Remove the log from the freezer and cut it into thin slices with a sharp knife.

Lay the spiral cookies on a baking tray lined with parchment paper. Bake them for about 12 to 13 minutes. Keep an eye on them, and remove them when the edges start to brown slightly.

Allow the cookies to cool on a wire rack. Enjoy them warm or store them for later!