Start by melting your butter in a medium saucepan over medium heat. Stir consistently until it turns golden brown and releases a nutty aroma.
Add the jumbo marshmallows to the browned butter and keep stirring. It might look like they won't blend at first, but trust the process—it takes about 5 minutes for the magic to happen.
Stir in the sweetened condensed milk until smooth, then remove from heat. Add the vanilla and enough blue food dye to achieve that Cookie Monster shade of blue.
Pour the blue marshmallow mixture over your rice krispie cereal and stir until everything is evenly coated.
Mix in ½ cup white chocolate chips, ¾ of the crumbled Chips Ahoy, and ¾ of the Oreos. Save the rest for topping—because more is always more!
Butter or line your 9x11 pan with parchment paper. Pour in the rice krispie mixture and spread evenly.
Sprinkle the remaining cookies and white chocolate chips on top, pressing them in gently.
Cover the pan and refrigerate for at least 20 minutes. Once set, cut into squares and marvel at your Cookie Monster-inspired masterpiece.