Prepare an 8 or 9 inch square baking pan with parchment paper. Spritz with nonstick cooking spray.
Place all of the ingredients EXCEPT the sprinkles into a microwave safe bowl. Heat on high for 1 minute. Stir vigorously to allow the chocolate to continue melting from the residual heat. Return to the microwave and heat in 15 second increments, if needed, stirring after each heating to avoid overcooking the chocolate.
Stir in the sprinkles, reserving some for the top.
Transfer the mixture into the prepared baking dish. Top with additional sprinkles.
Cover and chill in the refrigerator for 2 to 3 hours.
Use the parchment paper to lift the fudge from the baking dish. Cut into squares and serve.
To make on the stovetop:
In a saucepan over low heat, add the sweetened condensed milk, white chocolate chips, and butter. Stir constantly until melted.
Add the cookie mix and stir until well blended.
Stir in the sprinkles, reserving some for the top.
Transfer the mixture into the prepared baking dish. Top with additional sprinkles.