Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy. This should take about 3-4 minutes.
Add in the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the flour mixture to the wet ingredients, mixing until just combined.
Gently fold in the sprinkles, ensuring they are evenly distributed throughout the dough.
Scoop tablespoon-sized balls of dough and place them on the prepared baking sheet, leaving some space between each ball.
Bake for 10-12 minutes, or until the edges are lightly golden. The centers may appear soft, but they will firm up as they cool.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
While the cookies cool, prepare the frosting by whisking together the powdered sugar, milk, and vanilla extract until smooth. Adjust the consistency by adding more milk or sugar if needed.
Once the cookies are completely cooled, frost them with the prepared icing and sprinkle extra sprinkles on top for decoration.