For the mint cracker crust: Cover an acrylic base with parchment paper or an acetate sheet and create an 5⅜ × 6½–in/135 × 165–mm rectangle using ⅛-in/3-mm metal bars.
Melt the couverture and cocoa butter separately, then combine and stir to mix well.
Mix in the feuilletine flakes thoroughly.
Add the liquid cocoa butter and mix by with spatul