01 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside for later use.
02 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
03 - Mix in egg and vanilla extract to the butter mixture until thoroughly combined.
04 - Gradually incorporate dry ingredients into wet mixture, mixing just until dough forms. Avoid overmixing.
05 - Divide dough in half. Roll each portion between parchment sheets into 1/4-inch thick rectangles.
06 - Brush rectangles with melted butter, then sprinkle evenly with brown sugar and cinnamon mixture.
07 - Tightly roll each rectangle from the long side into a log. Wrap in plastic and refrigerate for 1 hour.
08 - Preheat oven to 350°F and line two baking sheets with parchment paper.
09 - Cut chilled logs into 1/2-inch rounds and place 2 inches apart on prepared sheets. Bake for 9-11 minutes until edges are golden.
10 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.
11 - Whisk powdered sugar, milk, and vanilla until smooth. Drizzle over cooled cookies and allow to set before serving.