Preheat your oven to 350°F (175°C). Line two baking sheets 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 using an electric mixer.
Add 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, baking powder, and salt. Gradually add the dry mixture to the wet mixture, mixing until just combined.
Fold in the rainbow sprinkles and white chocolate chips (if using), ensuring they are evenly distributed throughout the dough.
Using a tablespoon or a cookie scoop, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Press a few additional sprinkles onto the tops of the cookie dough balls for an extra fun look.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden and the centers look slightly underbaked.
Remove from the oven and let the cookies cool on the baking sheets for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve the cookies on a colorful plate or tiered dessert stand, and add extra sprinkles around the base for an eye-catching presentation.