Knead a small amount of modeling chocolate until it is pliable.
Roll out the modeling chocolate on a silicone baking mat until it is β in/0.3 cm thick. Cut out the leaves with the leaf cutter. Gather the excess modeling chocolate and wrap it tightly in plastic wrap so it does not dry out. Cover the leaf cutouts with a piece of plastic wrap.
Dust the leaf veiner with cocoa powder if you are using dark or milk modeling chocolate, or cornstarch if you are using white modeling chocolate.
Vein each leaf. Store on a parchment-lined sheet pan.
Once they are dry, brush off any excess cornstarch or cocoa powder.