Preheat oven to 375-degrees F. Line cookie sheets with parchment paper or silicone baking mats; set aside.
To measure out flour, spoon lightly into measuring cup, then with a straight edge level the flour even with the top of the cup. Add flour to a large measuring bowl. Whisk the baking powder and salt into the flour. Please note that the recipe calls for 1 tablespoon of baking powder. Set aside.
In the bowl of a stand mixer, with the whisk attachment beat together the butter and sugar until creamy, about 1 minute. Scrape down the sides of the bowl and add the milk and vanilla. Mix just until blended. Add the eggs, one at a time, mixing after each addition. Scrape down the sides of the bowl.
Change to the paddle attachment. Add the flour mixture to the bowl and mix on low speed just until incorporated, stopping to scrape down sides of bowl as needed. Do not over-mix. The dough should be soft and sticky, but malleable with floured hands. Allow dough to sit covered with plastic wrap for 5 minutes.
For each cookie, measure out a level tablespoonful of dough. (A one tablespoon scoop works well). With clean, floured hands lightly roll dough into a ball. Hands will need to be re-floured after about every fourth cookie to keep the dough from sticking to the hands. Place cookie dough balls on prepared pan, spacing 2-inches apart.
Bake for 7-8 minutes until set. The cookies should be resistant when touched lightly with a finger and light brown on the bottom. If light pressure from a finger causes the cookie to dent, the cookies should be returned to the oven for another minute or two. Underdone cookies will collapse as they cool and have a gummy texture.
Place baked cookies on a wire rack to cool. After cookies have cooled, glaze and decorate with sprinkles of choice.