In a heat-safe bowl, melt the cocoa butter over a double boiler
Remove from the heat, then sift in the milk powder, cocoa powder, and powdered sugar
Whisk until combined
Line a muffin tin with 6 cupcake liners
Pour enough melted chocolate into each cupcake liner so that just the bottoms are covered, then set in the fridge to cool
In a blender or food processor, blend together the graham crackers and powdered sugar until it becomes a powder
Add the powder to a bowl along with the peanut butter and mix with a spatula until a soft dough forms
Divide the dough into 6 balls
Remove the muffin tin from the fridge and add a ball into each liner
Press flat, making sure that it does not touch the sides of the cupcake liner, then pour more melted chocolate on top until the filling is fully covered
Leave in the fridge for 1-2 hours to set, then serve
