Step 2

Make the cookies: In a medium bowl, combine the flour, baking powder, baking soda, cinnamon and salt. Set aside.

Step 3

In the bowl of a stand mixer, cream the butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add the egg and vanilla and mix until combined.

Step 4

Reduce the mixer speed to low and add the flour mixture until just combined. Shape the dough into a disk and wrap it tightly in plastic wrap. Refrigerate for at least 2 hours, or up to 2 days.

Step 5

While the cookies are chilling, make the icing: In a stand mixer, beat the butter and confectioners' sugar until light and fluffy, 2 minutes. Add the salt, vanilla and 1 tablespoon of milk, and beat until smooth. Continue adding milk until the frosting is fluffy, then gently stir in the sprinkles.

Step 6

Preheat the oven to 350°. Line a cookie sheet with parchment paper and set aside.

Step 7

Lightly flour a kitchen surface, then place the dough on top and lightly flour the dough. Using a rolling pin, roll the dough to a ⅛-inch thickness. Use a small cookie cutter to punch out shapes and transfer them to the prepared baking sheet.

Step 8

Bake until the bottoms and edges of the cookies turn golden brown, 5 to 7 minutes.

Step 9

Remove the cookies from the oven and transfer them to a cooling rack. When they're completely cool, dip in the frosting and serve.