Preheat the oven to 350ºF.
Prepare a baking sheet by lining it with parchment paper.
In a large mixing bowl, cream butter and sugar together with a hand mixer.
Add egg, milk, and vanilla. Mix again until smooth.
Add flour, baking powder, and salt. Mix until dough forms.
Roll dough into 1-inch balls and place them onto a prepared baking sheet.
Using a glass dipped in flour, press each dough ball down until it is about 1/2-inchthick.
Bake for 9 minutes or until the tops begin to brown.
Allow cookies to cool completely.