In a mixing bowl, combine the all-purpose flour and salt, whisking together until evenly distributed. Set aside for later use.

In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, cream the softened butter and granulated sugar on medium speed. Beat until the mixture becomes light and airy, which should take around two minutes. Add the vanilla extract and the room-temperature egg, then continue mixing until smooth and fully integrated, about one minute. Gradually incorporate the flour mixture into the wet ingredients, mixing on low speed until just combined. Take care not to overmix to maintain the cookies' tender texture.

Evaluate the consistency of the dough. Test a small portion by transferring it into a piping bag fitted with a large open star tip, such as Ateco 826 or 827. The dough should be firm but pipeable. If it feels too stiff, add milk one teaspoon at a time, mixing well after each addition, until the desired texture is achieved.

Pipe swirls of dough onto ungreased baking sheets, spacing them approximately 2 ½ inches apart to allow for spreading during baking. Once all the dough has been piped, place the baking sheets in the refrigerator and chill the cookies uncovered for 30 to 40 minutes. This step ensures that the cookies maintain their beautiful piped shapes while baking.

Preheat the oven to 350°F (175°C). Once chilled, transfer the cookie sheets directly to the oven and bake for 12 to 15 minutes, or until the edges turn a light golden brown. Remove the cookies from the oven and allow them to rest on the baking sheets for about five minutes before carefully transferring them to wire racks to cool completely.

For decoration, melt the white chocolate chips in a microwave-safe bowl following the instructions on the packaging. To create a smoother consistency, you can stir in approximately one teaspoon of coconut oil per cup of melted white chocolate, though this step is optional. Use a spoon or piping bag to drizzle the melted chocolate over the cooled cookies. Immediately sprinkle the cookies with festive sprinkles to add a pop of color and holiday cheer.

Let the decorations set before serving or storing. Enjoy these buttery delights as a festive centerpiece or share them as a heartfelt holiday gift.