The cinnamon sugar filling is the flavorful heart of these cookies. Here’s how to make it just right:

• Gather Ingredients: You’ll need 4 tablespoons of softened unsalted butter, ⅓ cup of packed brown sugar, 1½ tablespoons of all-purpose flour, 2½ teaspoons of ground cinnamon, and a pinch of salt.
• Mix It Up: In a small bowl, combine the softened butter and brown sugar. Using a fork or a whisk, mix until the texture is smooth and creamy. The butter should be soft enough to blend easily but not melted.
• Add the Spice: Stir in the flour, ground cinnamon, and salt. These ingredients help thicken the filling, giving it consistency.
• Check Consistency: The filling should be thick but spreadable. Adjust with a little more flour if it’s too runny or a touch of melted butter if it’s too thick.

The base of these cookies should be as soft and inviting as the cinnamon filling they’re paired with. Focus on getting the dough texture just right:

• Cream the Butter and Sugar: Start with 1 cup of unsalted butter (softened but still cool to the touch) and mix it with 1⅓ cups of granulated sugar using an electric mixer on medium speed. This step creates a light and fluffy base.
• Introduce Eggs and Vanilla: Beat in 1 large egg, an additional egg yolk, and 1¾ teaspoons of pure vanilla extract. The egg yolk adds extra tenderness to the dough.
• Dry Ingredients: In a separate bowl, whisk together 2¾ cups of all-purpose flour, ¾ teaspoon of baking powder, 1 teaspoon of cornstarch, and ¼ teaspoon of salt.
• Combine: Gradually add the dry ingredients to the wet mixture. Mix on a low setting until just combined, forming a soft dough. Avoid overmixing to keep the cookies tender.

With both filling and dough ready, it’s time to assemble these delectable treats:

• Roll the Dough: On a floured surface, roll out the dough into a rectangle about ¼ inch thick. Keep it even to ensure uniform baking.
• Spread the Filling: Evenly spread the cinnamon sugar filling over the rolled dough, leaving a slight border around the edges to prevent over-spill.
• Roll and Chill: Starting from one of the longer sides, carefully roll the dough into a log. Wrap it in plastic wrap and chill it in the fridge for at least one hour to firm up the dough.
• Preheat and Slice: Preheat your oven to 350°F (175°C). Unwrap the chilled dough and slice it into ½-inch thick rounds.
• Bake to Perfection: Place the slices on a baking sheet lined with parchment paper, leaving space for spreading. Bake for 10-12 minutes, or until the edges are lightly golden. The center should remain soft.