Preheat the oven to 350° F. Line cookie sheets with aluminum foil and spray with cooking spray or line with parchment paper or silicone mats. Set aside.

Cream together the butter, sugar, and brown sugar in the bowl of an electric mixer, until smooth and creamy. Add the egg and vanilla and mix until smooth. In a small bowl, mix together the flour, baking soda, and salt, and stir until just combined. Slowly add the dry ingredients into the wet ingredients, mixing on low to medium, until well combined.

Fold in white chocolate chips and rainbow sprinkles, saving some to top the cookies with at the end. For large cookies, scoop 1/4 cup portions of dough on the pan. If you make them this large, only put about 6 on each pan. For smaller cookies, drop the dough in smaller rounded tablespoons, putting 12 on each pan.

Bake for about 10-12 minutes (larger cookies will take longer) until the edges of the cookies look golden brown. Sprinkle the top of the bars with the remaining white chocolate chips and rainbow sprinkles. Let the cookies cool for about 15-20 minutes before serving. Enjoy!