Mix 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 in a bowl. Blend until smooth and set aside.

Cream 1 cup of unsalted butter with 1⅓ cups of granulated sugar in a large bowl until light and fluffy.

Add 1¾ teaspoons of pure vanilla extract, 1 large egg, and 1 large egg yolk, mixing until well combined.

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.

Gradually add the dry mixture to the wet mixture, stirring until just combined.

Roll the dough into a log about 10 inches long and spread the cinnamon filling evenly over the surface.

Carefully roll the dough back up and wrap it in plastic wrap. Chill in the refrigerator for at least an hour.

Preheat the oven to 350°F (175°C).

Once chilled, slice the dough into ½-inch thick rounds and place them on a baking sheet lined with parchment paper.

Bake for 10-12 minutes, or until the edges are lightly golden, but the centers are still soft.

Allow them to cool slightly on the baking sheet before transferring to a wire rack.