Line an 8 inch square pan with foil and butter the foil.
Pour cereal in a mixing bowl.
Heat butter over medium in a small saucepan until it starts to melt, then stir in corn syrup and heat until mixture starts to boil.
Remove from heat and stir in the chocolate chips. Stir until melted, then add vanilla.
Pour over the cereal and stir to coat, then stir in the marshmallows. Dump mixture into the pan and press down lightly with another sheet of buttered foil.Wipe the saucepan clean and add the milk chocolate.
Heat on low, stirring constantly, until it’s just barely melted (don’t overheat), then drizzle over the cereal bars. Chill for a few hours or until set, then lift from pan and cut into bars. I like trimming the edges and making 8 big bars, but you can cut them whatever size you like.
