Preheat oven to 350 degrees and line a 9 x 13 pan with parchment paper.
Beat softened butter, brown sugar, and granulated sugar with a hand or stand mixer. Add eggs, vanilla extract, and milk until combined.
1 cup Butter, 1 cup Brown Sugar, 1/2 cup Granulated Sugar, 2 Eggs, 1 1/2 teaspoon Vanilla, 1/2 Tablespoon Milk
Whisk together flour, salt, and baking soda in a separate bowl. Gradually stir dry ingredients into the wet until completely combined.
2 1/2 cup Flour, 1/2 teaspoon Salt, 1 teaspoon Baking Soda
Fold in white chocolate chips and sprinkles. Spread evenly into the prepared baking pan. Sprinkle additional sprinkles over the top of the batter.
1 cup White Chocolate Chips, 2 Tablespoon Sprinkles
Bake for 15-20 minutes or until a toothpick inserted in the center comes out clean. Cool completely before serving.