Heat 150ml cream until simmering, then stir in dark chocolate pieces until smooth.
Cool for 15 minutes, add remaining 150ml cream, and whisk to soft peaks.
Whisk one egg white to stiff peaks, add caster sugar to create meringue, and fold into chocolate mixture.
Chill mousse until set.
Mix butter, icing sugar, and vanilla into a paste, then whisk in egg whites.
Fold in flour gradually with a wooden spoon.
Mix cocoa powder into one-sixth of the paste and rest both mixtures for 30 minutes.
Preheat oven to 180°C and line a tray with parchment.
Spread plain paste over templates to form nine shapes.
Pipe chocolate paste patterns onto the shapes and bake for 5-6 minutes.
Drape warm tuiles over a rolling pin to create curved shapes immediately after baking.
Bake nine more plain tuiles and roll around spoon handles to form cigars.
Dip set cigars into melted plain chocolate.
Flatten a spoonful of paste to 8cm circles and bake to form baskets over ramekins.
Fill baskets with mousse and serve with curved and cigar tuiles.