In a large pan, add marshmallow fluff and butter. Heat on medium low until butter melts.
Remove from heat and stir until mixture is smooth.
Add in the cereal.
Melt the chips by heating in the microwave in a microwave safe bowl in 30 second bursts until melted and smooth. Fold in melted chocolate and raisins .
Press mixture into baking dish. Cover with cling wrap and press down. Allow to chill for 2-3 hours before cutting.
Cut into 1”x6” bars. Drizzle onto the cereal bars and serve.