Preheat the oven to 180°C. Grease a 25-cm non-stick tart tin with a removable base lightly. Combine the crumbs, egg white and honey. Press crumb mixture onto bottom and side of tart tin to make a crust. Bake 10 minutes. Cool.
Put 3 tbsp water in a saucepan; sprinkle on gelatine. Leave for 1 minute. Stir over a low heat until gelatine dissolves, about 2 minutes. Remove from heat.
Mix sugar and cocoa in a large bowl. Stir in milk and vanilla essence until cocoa dissolves. Stir in the gelatine. Cool.
Whip cream until stiff. Fold three-quarters of the whipped cream into cooled cocoa mixture until blended. Pour into the crust. Swirl remaining whipped cream in the centre. Refrigerate for 2 hours or overnight to let mousse set.
Dust with cocoa powder and decorate with chocolate curls. To make curls, the chocolate must be at room temperature. Draw the blade of a vegetable peeler across it, pressing down firmly. Lift curls into place with a skewer.
Gelatine must be softened and dissolved with care because it can easily become lumpy when added to other mixtures. Sprinkle powder evenly on top of liquid to soften. Do not stir gelatine while it is in the process of dissolving.