Butter and flour the sides of the sandwich tins and line the bottom with a disc of non-stick (silicone) cooking paper. Set the oven at 190 degrees C. or Mark 5. Whisk the egg whites until stiff with a rotary or electric beater, add the sugar 1 tbs at a time and continue beating until the mixture is very stiff and stands in peaks. Whisk in the vanilla essence and vinegar, then fold in prepared nuts. Divide the mixture between the two prepared tins and smooth the top with a palette knife; bake 30-40 minutes but no longer. The top of the meringue will be crisp and the inside soft like a marshmallow. Turn onto wire racks to cool.
Watchpoint: Always fill meringue at least three hours before serving; cake will then cut into portions without splintering. Whisk the cream, sweeten and flavour with extra sugar and vanilla; use about two thirds to fill meringue. Dust top with icing sugar and use the remaining cream to shape, or pipe rosettes on the top. Serve the Melba sauce separately, (see below).