Unroll the pie crust and spread the soften butter edge to edge in an even layer
Evenly sprinkle the cinnamon sugar over the butter,
Tightly re-roll the pie crust and place in the freezer for 15 minutes
Using a very sharp knife slice into ⅛" rounds and place on the parchment paper lined baking sheet. These do not spread so you don't need to leave a lot of space between rounds.
Top each round with approximately 1/4 teaspoon of dark brown sugar. Use the back of the measuring spoon to press the sugar down into an even layer. It doesn't not have to be perfect.
Bake for 8-9 minutes in the 450°F preheated oven, the sugar should be caramelized on top and edges of the pie crust should be slightly browned.
Allow to cool on the baking sheet for 1-2 minutes and transfer to a baking rack to cool. The sugar will be extremely hot and could burn you.