Beat eggs with sugar till thick.
Melt chocolate and mix in.
Fold in flour, cocoa and butter.
Bake in a greased and floured round tin or recess flan tin.
Bake for 20 minutes on 180C or till sponge shrinks away from the side of tin.
Cool. For the mousse, put chocolate, water and sugar in a pan and stir over low heat till it melts.
Transfer to a bowl and mix in yolks and butter.
Add essence and dissolved gelatin.
Lastly fold in the cream.
Spread mousse over cooled sponge.
Chill till sets. Pipe a swirl of cream to decorate once mousse has set.