Prep your space by clearing room in the refrigerator for cookies to chill and preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.

Cream the soft European salted butter in a stand mixer at medium speed until smooth. Gradually add granulated sugar and salt, mixing until fluffy and light.

With the mixer on low, add egg yolks, vanilla extract, and whole milk to the mixture, mixing until well combined and smooth.

Whisk together all-purpose flour and cake flour in a separate bowl, then gradually mix into the wet ingredients until just combined.

Transfer dough to a piping bag with a star tip, and pipe 2-inch circles on lined baking sheets, spacing them at least 2 inches apart.

Chill the piped cookies in the refrigerator for 20-30 minutes, then bake in the preheated oven for 10-15 minutes until edges are lightly golden.

Allow cookies to cool on baking sheets for 5 minutes, then transfer to a wire rack to cool completely.