Preheat your oven to 375°F. Line 2 large baking sheets with parchment paper or cookie mats.
Sift the flour, baking powder, and salt in a medium bowl.
In a large bowl, use an electric mixer to beat the softened butter until smooth with no lumps. Add the granulated sugar and beat until well combined and fluffy. Mix in the egg yolks and vanilla extract.
Add half of the sifted dry ingredients, then mix in the whole milk, followed by the rest of the dry ingredients. Mix until the dough comes together.
Pipe the cookie dough: Add an extra large open star piping tip to a large, durable piping bag. Fill the bag with about half a cup of dough at a time and pipe assorted shapes onto the lined baking sheet. Leave ½-1 inch between the piped shapes.
Bake: Bake the cookies, one sheet at a time, for 7-8 minutes. Allow to cool completely on the baking sheet before removing.
Decorate: Dip one side of the cookies in melted chocolate and add some sprinkles to decorate.
Store the cookies in an airtight container at room temperature for 4-5 days.