Method

Pre-heat the oven to 180c/ 350f/ gas mark 4.
Grease 2 x 20 cm (8 inch) sandwich tins with butter and line the bases with a circle of greaseproof paper .
Place the egg whites in a spotlessly clean mixing bowl or freestanding mixer bowl (washing and drying then wiping with a little lemon juice of vinegar usually works) then whisk  with an electric whisk until the egg whites have reached stiff peaks and then gradually whisk in the sugar, 1 tablespoon at a time. Continue whisking till it holds its shape (for around 5–10 minutes).
When ready gently fold in vanilla, vinegar and hazelnuts.
Gently spoon the mixture into tins and carefully level bake in the oven for 45-50 minutes until risen, set and lightly golden. Remove from the oven and allow to cool in the tins on cooling racks. You can make the meringues in advance and keep them in an air tight tin for 1 week.
Once cool, carefully remove the meringues from the tins. Lightly whip the double cream and sandwich the meringues with it then keep in fridge until ready to serve. It’s light and crisp on day one but goes soft and chewy by day 2 (which is when we as a family prefer to serve it). Top with berries or flowers if using.