Pre‑prep: In a medium bowl whisk together the flour, baking powder and salt. Set aside.

In a large bowl (or stand mixer with paddle attachment), beat the softened butter and granulated sugar together on high speed until completely smooth and creamy (about 2 minutes). Then add the egg and vanilla extract, and beat until combined (~1 minute), scraping down the sides and bottom of the bowl as needed.

On low speed add the dry ingredient mixture to the wet mixture. Mix until combined; the dough will be a bit soft. If it seems too sticky for rolling out, add 1 additional tablespoon of flour.

Shape & roll: Divide the dough into two equal parts. On a floured surface (or on floured parchment/silicone mat) roll each portion into a rectangle about 9 × 7 inches (~23×18 cm) and about ¼‑inch thick.

Spread about 1 Tablespoon melted butter onto each rectangle. In a small bowl mix the granulated sugar and cinnamon together, then sprinkle evenly over each buttered rectangle.

Starting with one long end, slowly and tightly roll up each rectangle into a 9‑inch log. If the dough cracks a little, use your fingers to smooth it. Some cracking is okay. Wrap each log loosely (e.g. in plastic wrap) and chill for at least 2 hours (or you can freeze up to 3 months).

Preheat your oven to 350°F (177°C). Prepare a large baking sheet by lining it with parchment paper or a silicone baking mat.

Remove the chilled dough logs from the fridge. Cut each log into slices about ½‑inch thick. Place the slices onto the baking sheet spaced about 2 inches apart.

Bake for 10‑11 minutes, or until the edges are lightly browned. Remove from the oven and let cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before icing.

Make the icing: Whisk together the confectioners’ sugar, milk, and vanilla extract until smooth. Drizzle over the cooled cookies.

Store: Keep cookies fresh by storing them in an airtight container at room temperature for up to 5 days.