Boil water and sugar in a pan while wiping sides with a wet brush to prevent crystallization.
Beat egg whites to stiff peaks when the sugar mixture reaches 110°C.
Remove the sugar syrup from heat once it reaches 121°C.
Pour the syrup slowly into the egg whites while beating on a low setting.
Beat the mixture slowly for up to 15 minutes until almost cold.
Fold in the hazelnuts and transfer the meringue to a piping bag.
Place sponge on a plate and top with scoops of vanilla and toffee ice cream.
Pipe meringue over the ice cream and glaze using a blowtorch or a very hot oven.
Heat cream, sugar, and butter in a pan, then whisk in syrup and treacle to make the sauce.
Slice the Baked Alaska into wedges and drizzle with warm toffee sauce.