Beat softened butter with both sugars until light and fluffy. Add eggs, milk, and vanilla, mixing until smooth and creamy. This mixture forms the flavorful base of your cookies.
In another bowl, whisk flour, baking powder, and salt together. Slowly combine the dry mixture into the wet ingredients until dough forms. Mix gently to avoid tough cookies.
Wrap the dough and refrigerate it for at least 1–2 hours. Chilling firms the dough, making it easier to roll and helps cookies keep their shape.
Preheat the oven to 350°F (175°C). Roll dough to about ⅛-inch thickness and cut heart shapes. Place on lined baking sheets and bake 10–12 minutes until edges are lightly golden.
Transfer cookies to a cooling rack and allow them to cool completely. Once cooled, frost and decorate with sprinkles while icing is soft.