For the cookies: Crumble the cookie dough into a large bowl and let sit until softened, about 10 minutes. Meanwhile, line a 9-inch square cake pan with plastic wrap.
Add the flour and baking powder to the cookie dough and mix by hand to combine. Transfer the dough to the prepared pan. Add another piece of plastic on top and press the dough into an even layer. Refrigerate until firm, about 15 minutes.
Combine the butter, brown sugar, granulated sugar, cinnamon and salt in a small bowl.
Remove the top layer of plastic from the dough, then transfer the dough on top of the bottom layer of plastic to a work surface. Spread the butter mixture over the dough, leaving a 1/4-inch border. Roll the dough into a log, using the plastic wrap to keep it tight. Wrap the cylinder in plastic and freeze until solid, about 2 hours.
When ready to bake, preheat the oven to 350 degrees F and line 2 baking sheets with parchment.
Cut 1/4 inch off each end of the cylinder with a very sharp knife to reveal the cinnamon swirl. Cut the cylinder into about 1/2-inch-thick slices. Arrange the slices about 1 1/2 inches apart on the prepared baking sheets. Bake until just cooked and barely golden on the edges, about 15 minutes. Let the cookies cool on the baking sheets for 10 minutes, then transfer to a wire rack to cool completely.
For the glaze: Combine the confectioners' sugar, milk, butter and salt in a small bowl. Whisk until smooth. Transfer the mixture to a small piping bag and pipe the icing back and forth in thin stripes over the cookies.
Copyright 2019 Television Food Network, G.P. All rights reserved.