Grease a 9x13 pan with extra butter; set aside. Melt butter in a small microwave safe bowl. Pour into a large mixing bowl and place marshmallows right over top. Mix together to coat marshmallows with melted butter.
Place bowl in microwave and heat for 30 seconds; remove from microwave and stir. Heat for 30 more seconds and stir again until marshmallows are melted. Add cake mix and stir well.
Pour rice krispies into melted marshmallows mixture. Stir until cereal is coated. Press treat mixture into greased pan, getting your hand wet first to avoid get the mixture stuck on your hand. Sprinkle with desired amount of sprinkles. Cover with aluminum foil and place in the fridge for at least one hour.
Cut treats into 20-24 squares and place upside down on wax paper. Pour white chocolate chips into a microwave safe bowl; heat for 45 seconds then stir. Heat for another 45 seconds and stir again, until chocolate is melted.
Dip the bottom of each treat into the white chocolate and place upside down on the wax paper to cool. Serve when chocolate has completely cooled. Enjoy!