First, in a big bowl, use an electric mixer to beat the softened butter and sugar together until they're light and fluffy, about a minute. This simple start makes your cookies wonderfully tender!
Next, add the vanilla extract and room-temperature eggs, beating for another minute. Then, gently mix in the flour, baking powder, baking soda, and salt. Beat on low speed for 1-2 minutes until the dry ingredients are just combined; don't overmix! It might look a bit crumbly. Pour in the milk and continue mixing on low until you have a smooth, soft dough. Cover the dough and pop it in the fridge to chill for at least an hour. This step is key for perfect, less-spreading cookies!
While your dough chills, get your baking sheets ready by lining them with parchment paper – makes cleanup a breeze! Pour your colorful Christmas sprinkles into a shallow dish. Once the dough is nicely chilled, scoop out about 1-2 tablespoons per cookie, roll it into a neat ball, and then gently roll it in the sprinkles to coat evenly. Place these festive cookie balls about an inch apart on your prepared baking sheets. Bake in a preheated oven at 400°F (200°C) for 6-9 minutes, or just until the edges barely start to turn a light golden. Remember, a slightly underbaked cookie stays soft and chewy!
As soon as they're out of the oven, quickly move the warm cookies to a wire rack to cool completely. Leaving them on the hot baking sheet can make them overcook and become hard. Enjoy these incredibly easy-to-make, delightful Christmas treats!