In a bowl, using an electric mixer, beat cream and vanilla until firm peaks form.
Unroll sponge roll on baking paper (roll may crack slightly). Drizzle with cherry liqueur. Spread over cream mixture. Sprinkle with cherries. Roll up to enclose the cream filling, using baking paper to help guide cake if needed. Chill for 30 minutes until firm.
Meanwhile, to make ganache; in small saucepan, bring cream to just below boiling. Pour over chocolate in heatproof bowl. Wait for 2 minutes and stir until smooth. Chill for 15 minutes to thicken slightly.
Spread ganache over roll. Press on flake shards. Attach marshmallows to milk bottle lollies with melted white chocolate, press on red cachous and dust log and mushrooms with combined cocoa and icing sugar.
For a special festive touch, dust with edible glitter before serving.Note