Make space in the refrigerator and prep the baking mats. Make room in your refrigerator for a baking sheet so the shaped cookies can chill for 20-30 minutes. Without chilling, the piped cookies may over-spread. Line two baking sheets with parchment paper or a silicone baking mat. Set aside.
Cream butter, sugar salt. In the bowl of a stand mixer fitted with a paddle attachment, cream butter on medium speed until smooth. With the mixer still running on low, slowly add in sugar and salt. Mix on medium speed until light and fluffy.
Incorporate egg yolks, vanilla, and milk. While mixing, add egg yolks, vanilla, and milk. Continue to mix on medium speed until well combined. Scrape down the sides of the bowl for thorough mixing.
Mix dry ingredients and add into mixture. In a medium-sized mixing bowl, whisk the flour, and cake flour. Add flour mixture to mixer in two additions, and scrape down the sides of the bowl. Mix on low speed until combined and no traces of flour. If the batter is too thick to pipe, add another tablespoon of milk to soften.
Pipe the cookies. Transfer cookie batter to a large piping bag with fitted a ½-inch open star tip. Pipe 2-inch cookies (rosettes, pretzels, circles, squares) on a prepared baking sheet. Space cookies at least 2-inches apart. If desired, sprinkle the dough with festive sprinkles and/or coarse sugar. Chill in the refrigerator for 20-30 minutes.
Prepare the oven. Preheat oven to 350°F. Make sure the baking rack is in the middle of the oven.
Bake. Bake for 10-15 minutes or until the edges are JUST lightly golden brown. Let cookies cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool to room temperature.