Preheat oven to 100°C and whisk egg whites with lemon juice and sugar to create a stiff meringue.
Pipe meringue droplets onto parchment paper and bake for 45 minutes until crisp.
Puree the tinned rhubarb in a food processor.
Heat half the rhubarb puree and dissolve the soaked gelatine into it before cooling.
Whip the cream slightly and chill.
Whisk sugar, glucose, and 50ml water to 116°C and stream into whisked egg whites for Italian meringue.
Fold the gelatine rhubarb mixture, whipped cream, and remaining puree into the Italian meringue.
Pipe the mousse into a bag and chill in the fridge for 45 to 60 minutes.
Blend cone ingredients with 250ml water and cook in a waffle maker until golden before rolling.
Melt white chocolate buttons in the microwave using 10 second bursts until smooth.
Seal the bottom of each cone with a small amount of melted white chocolate.
Create colored chocolate sheets on acetate sprinkled with popping candy and chill for 25 minutes.
Peel acetate to break chocolate into flame-like shards.
Boil glucose, honey, sugar, and 100ml water to 154°C, then whisk in bicarbonate of soda.
Pour honeycomb into a tray to cool and break into pieces.
Make a custard with milk, cream, yolks, and sugar by cooking on low heat until thickened.
Whisk yoghurt into cooled custard and churn in an ice cream machine.
Layer mousse, honeycomb, and meringue into cones, topping with ice cream and chocolate shards.