Blend 4 tablespoons of softened unsalted butter with 1/2 cup of packed brown sugar until creamy and smooth. Mix in 1/4 cup of all-purpose flour, 2 teaspoons of ground cinnamon, and a pinch of salt.

Cream together 1/2 cup of softened unsalted butter and 1/2 cup of granulated sugar until light and fluffy, about 2-3 minutes. Beat in 1 egg, 1 yolk, and 1 teaspoon of vanilla until well incorporated.

Whisk together 1 3/4 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of cornstarch, and 1/4 teaspoon of salt. Gradually add to the wet mixture, stirring until combined without overmixing.

Roll out the dough on a floured surface into a rectangle about 1/4 inch thick.

Spread the filling evenly across the rolled-out dough, leaving a border. Roll the dough into a log shape and refrigerate for at least 1 hour.

Preheat oven to 350°F (175°C). Slice the log into ½-inch rounds and place on a parchment-lined baking sheet. Bake for 10-12 minutes until edges are lightly golden.

Cool cookies on the baking sheet for 5 minutes before transferring to a wire rack.