2Cream the butter and powdered sugar together until light and pale in color.
3Add the salt (if using unsalted butter), vanilla extract, and milk, then cream again until smooth.
4Sift the flour into the mixture and mix until it forms a thick paste-like dough.
5Transfer the dough into a piping bag fitted with a flower/star nozzle and pipe out zigzag shape cookies onto a baking tray lined with parchment paper.
6Bake at 170°C (340°F) for 15-20 minutes, or until the edges are lightly golden.
7Let the cookies cool completely on a wire rack before serving.
8After the cookies cool down completely, dip them in melted dark chocolate and put on parchment paper.
9If you're in cold weather, they should set at room temperature, otherwise refrigerate for 5 minutes and devour.