She says this quantity will serve 8-10, but with the chocolate filling it is very rich and will serve more.

Mix cornflour and sugar. Put egg whites in mixer bowl with pinch of salt. Whisk at low speed until frothy, then increase speed and whisk until mixture is makes stiff but glossy peaks. Start adding sugar/cornflour a bit at a time, beating till stiff after each addition. When all mixture had been added, beat in vinegar and vanilla.

Spoon or pipe into 2 8" circles on silicon paper lined baking trays. Have oven heated to 300F, 150 °C. Turn down to 275F, 140 °C. Put cakes in and bake for 45 min to 1 hour, swapping over position halfway through. They are ready when top is firm and crisp to touch.

Filling: Melt some chocolate and mix with a beaten parev whip. Should be quite dark brown and taste definitely of chocolate.

When meringues are cool sandwich together with filling. Can be served from fridge or freezer.