Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a medium bowl, combine the flour, baking powder, baking soda, salt, and ground cinnamon. Whisk together until well blended.
In a large mixing bowl, beat the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes.
Add the egg and vanilla extract to the butter mixture and mix until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Using a tablespoon, scoop out the dough and roll it into balls. Place them on the prepared baking sheet, leaving space in between for spreading.
Gently press down on each dough ball to flatten slightly.
Bake in the preheated oven for 8-10 minutes, or until the edges are set and the tops are lightly golden.
While the cookies are baking, prepare the icing by whisking together the powdered sugar, milk, and vanilla extract until smooth.
Once the cookies are done, remove them from the oven and let them cool on the baking sheet for a couple of minutes before transferring them to a wire rack to cool completely.
Drizzle or spread the icing over the cooled cookies and let it set before serving.
Notes
Arrange the cookies on a beautiful serving platter and sprinkle a little extra ground cinnamon on top for an elegant touch. Serve with a glass of milk for a classic pairing!