Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a separate large bowl, cream together the softened butter and granulated sugar until light and fluffy. Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Stir in the milk until the dough comes together. The dough should be soft but not sticky.
In a small bowl, combine the brown sugar, ground cinnamon, and softened butter. Mix until a smooth paste forms.
On a lightly floured surface, roll out the cookie dough into a rectangle about 1/4 inch thick. Spread the cinnamon sugar mixture evenly over the dough.
Starting from one long end, tightly roll up the dough into a log. Use a sharp knife to cut the log into 1/2-inch thick slices.
Place the cookie slices onto the prepared baking sheet, leaving about 2 inches between each cookie.
Bake for 8-10 minutes, or until the edges are lightly golden brown.
Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
While the cookies are cooling, prepare the optional glaze by whisking together powdered sugar and milk until smooth. Drizzle the glaze over the cooled cookies.
