Preheat your oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper, leaving some overhang for easy removal.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large mixing bowl, cream the softened butter, granulated sugar, and brown sugar until light and fluffy using an electric mixer, about 2-3 minutes.
Beat in the vanilla extract and eggs until well combined.
Gradually add the dry flour mixture to the wet ingredients, mixing just until combined. Be careful not to over-mix.
Gently fold in the sprinkles and white chocolate chips (if using) until evenly distributed.
Spread the cookie dough evenly into the prepared pan, smoothing the top with a spatula.
Bake in the preheated oven for 20-25 minutes or until the edges are golden brown and a toothpick inserted in the center comes out clean.
Allow the cookie bars to cool in the pan for about 15 minutes, then lift them out using the parchment paper and let them cool completely on a wire rack.
Once cooled, cut into squares or rectangles and serve!