1. Preheat oven to 180C or 160C fan. Grease and line base and sides of two 20cm sandwich cake pans.

2. Using an electric mixer, beat eggwhites until firm peaks form. Add 1 cup of sugar, 1 tablespoon at a time, beating until thick and glossy. Add vanilla and vinegar and beat for 20 seconds.

3. Gently fold though hazelnuts. Divide mixture evenly into prepared pans, smoothing top with a spatula. Bake for 35 minutes, until pale golden and firm. Cool in pans before turning out.

4. Meanwhile, make chocolate sauce. Place chocolate and 1/2 cup water in a small saucepan on low heat and stir until melted. Add remaining sugar and another 3/4 cup water and stir frequently until dissolved. Simmer for 10 minutes, until thickened. Remove from heat and cool.

5. Whip cream and stir through 1/4 cup of chocolate sauce. Spread onto one meringue round and top with other round. Cover and refrigerate overnight or for at least 1 hour until ready to serve. Dust with icing sugar and serve cut into wedges drizzled with remaining chocolate sauce.

Tip: Keep an eye on this cake as it nears the end of baking - the high oil content of the hazelnuts can make the cake burn more readily