Let the butter soften at room temperature in the bowl of a stand mixer. When soft, beat until billowy and light. Add the sugar, and mix again until well integrated. Add the eggs and milk, and mix until uniform in color. Combine the flour, baking powder, and salt in a separate bowl, then gradually stir into the butter mixture, either by hand, or with the mixer on low. Divide the dough into four, shape into flat disks, wrap in parchment or plastic, and refrigerate for an hour or two.
