Cream together softened butter, powdered sugar, and brown sugar until light and fluffy (3 to 4 minutes).

In a separate bowl, whisk together flour, baking powder, salt, and cream of tartar.

Gradually mix dry ingredients into wet ingredients until a soft dough forms.

Place down saran wrap on your counter and dump your dough onto it. Shape into a square. Wrap well and refrigerate for 1 hour to firm up slightly. You want it chilled but not firm. If it is too cold the filling will harden and you will not be able to spread it evenly.

Do this right before you are about to roll out your dough.

Melt the 30g butter in a small microwave-safe bowl or small saucepan.

Let the melted butter cool for 2 to 3 minutes (warm but not hot).

Add 8g cinnamon, 2g vanilla extract, and 8g flour, mixing until you have a thick, spreadable paste.

Add in your 15g of softened butter, mixing until cohesive. (The mixture should be thick like peanut butter)

Remove cookie dough from refrigerator after 1 hour rest.

Roll the dough into a rectangle measuring 12 inches x 9 inches on a lightly floured surface.

Using an offset spatula or the back of a spoon, spread the cinnamon-butter mixture evenly over the entire dough surface in a thin layer, leaving a 3/4 inch border along one long edge. (You may not need all the filling)

Work quickly but gently to ensure even coverage, the layer should be thin enough that you can still see some dough through it.

Starting from the long edge opposite the border, roll the dough tightly into a log, applying gentle pressure as you roll.

When you reach the border edge, press down to create a thinner edge. You can also lightly brush it with water or beaten egg to help it seal.

Roll the log onto the seam. Gently press the seam firmly along the entire length of the log.

Gently roll the log back and forth on the counter 2 to 3 times to compress and ensure good adhesion between layers.

Wrap the log tightly in plastic wrap.

Refrigerate for at least 4 hours or overnight (8 to 12 hours) for fermentation and proper firming.

Preheat oven to 325°F (165°C).

Line baking sheets with parchment paper.

Remove dough log from refrigerator and let sit at room temperature for 5 minutes (no longer).

Using a sharp knife, slice into 1 inch thick rounds.

For knife method: use a gentle sawing motion without pressing down.

Place cookies cut-side down on parchment-lined baking sheet, spacing 2 inches apart.

Let sliced cookies rest at room temperature for 10 minutes before baking (allows layers to settle and bond).

Bake at 325°F for 16 to 18 minutes until edges are just turning golden but centers still look slightly soft.

Let cool on the baking sheet for 10 minutes before transferring to a wire rack.

Once cool, you can optionally create the below stabilized cream cheese frosting to drizzle over the cookies.

Cut the cold cream cheese into small cubes and beat in a bowl until smooth, about 1 minute.

Add the slightly softened butter and beat until completely combined with no lumps, about 2 minutes.

Gradually add the sifted powdered sugar and cornstarch, mixing on low speed.

Add the vanilla and salt, then increase to medium speed and beat until light and fluffy, about 2 to 3 minutes.

If the frosting is too stiff, add heavy cream 1/4 teaspoon at a time until you reach your desired consistency.

Add frosting to a ziplock bag.

Trim off corner, the closer to the edge the smaller your drizzle will be.

Drizzle however you want over top on the dippers.

Sprinkle a WHISPER of cinnamon over the icing.

Rest your frosted cookie for at least 2 hours to allow the frosting to set properly.