In a medium bowl, whisk together the flour, baking powder, and cinnamon (if you’re feeling that cozy holiday vibe). This step keeps every cookie soft and evenly textured. Set it aside while we move on to the fun part.

Beat the salted butter with the brown sugar and granulated sugar until it’s light, fluffy, and smelling amazing. A hand mixer or stand mixer works great. Scrape down the sides a couple times so everything gets mixed in, you don’t want any sugar hiding out!

Incorporate the egg and vanilla, stirring until the mixture is silky and well combined. Your dough should feel soft, silky, and ready to be shaped.

Slowly fold in the flour mixture, just until everything combines. Don’t overmix, we want tender, buttery cookies, not tough ones. You’ll end up with a soft, slightly sticky dough that’s perfect for rolling.

Divide the dough in half. Keep one half as your vanilla layer, and stir the Dutch-process cocoa powder into the other half until it’s rich and chocolatey.

Lightly flour your two pieces of parchment paper and roll each dough half into a rectangle, about 9″ x 12″, keeping each on its own parchment.

Place the chocolate rectangle on top of the vanilla one so the vanilla wraps around it. Carefully peel off the top parchment and trim any uneven edges. Roll it up gently, like a jelly roll, pressing lightly so the layers stay snug but not squished.

Wrap the dough log tightly in plastic wrap and freeze for about an hour. Chilling keeps the slices neat and prevents the chocolate from blending into the vanilla layer, plus, it makes slicing much easier.

Set the oven to 350ºF (175ºC) and line a baking sheet with parchment for an easy, nonstick surface. Slice the chilled log into thin rounds and space them apart on the sheet. Let them bake for about 8–9 minutes, watching for the edges to turn a light golden. The centers may still look soft, and that’s perfect, they’ll firm up as they cool. Enjoy!