Line a 9x6 inch (23x15cm) baking pan (I think also an 8 or 9 inch square baking dish would do) with parchment paper. Set aside.
Melt the dark chocolate and spread on the baking dish (swirl the chocolate to cover the bottom). Leave at room temperature.
Melt 5 ounces (145 grams) of milk chocolate and butter, when almost melted remove from heat and stir until smooth, then fold in the Rice Krispies a little at a time and combine, spoon the Rice Krispie mixture evenly on top of the first layer. Let sit at room temperature.
Melt remaining 2½ ounces (73 grams) of milk chocolate, then pour on top of the 2nd layer, and spread as evenly as possible.
Let sit for at least 2-3 hours in the fridge. Then cut into bars. Enjoy!
Notes
Place the slices in an airtight container in single layers, with parchment paper between the layers. The container can be stored at room temperature (if your house is cool) for up to three days, or refrigerate for up to a week.They can also be frozen in a freezer safe container, with parchment paper separating the layers, they will keep for up to 6 weeks in the freezer.