How to Make It
Preheat oven to 325°.
Place butter in the bowl of a stand mixer, fitted with the paddle attachment; beat 2 to 3 minutes. Add 2/3 cup condensed milk and vanilla to bowl; beat 2 to 3 minutes or until combined and fluffy.
Add flour, baking powder, and salt to bowl; mix at low speed until combined, scraping down sides of bowl with a rubber spatula as necessary. Refrigerate dough at least 1 hour.
Divide the dough into 24 equal portions (about 1-ounce each); roll portions into balls and flatten slightly. Arrange dough portions 2 inches apart on parchment paper-lined baking sheets. Bake at 325° 12 to 15 minutes or until golden, rotating pans halfway through baking.
Allow cookies to cool 5 minutes on baking sheets; gently transfer cookies to a wire rack to cool completely.
While cookies cool, combine cream cheese and remaining condensed milk in the bowl of a stand mixer fitted with the whisk attachment; beat until combined and smooth. Spoon the glaze evenly over the cooled cookies; sprinkle evenly with sprinkles, if desired.