Preheat the oven to gas 3, 170°C, fan 150°C.
To make the meringue, beat the egg whites in a clean bowl with an electric whisk for 4 minutes until they form soft peaks. Add the sugar, 1 tbsp at a time, beating after each addition until it is all combined. Whisk for 3 minutes more, then add the white wine vinegar and cornflour, and then whisk for a further minute more.
Line a baking tray with nonstick baking paper and, using a pencil, mark out a circle 25cm (10in) in diameter in the middle. Spoon large, equal dollops of the meringue mix along the circle line to form a wreath shape. Put the meringue in the oven and immediately reduce the temperature to gas 1, 140°C, fan 120°C. Cook for 1 hour 30 minutes, then turn off the oven and leave the wreath in there to cool completely (overnight). Carefully peel off the baking paper and transfer to a serving platter.
To make the chocolate sauce, melt the plain chocolate, butter and double cream in a heatproof bowl over a pan of barely simmering water. Stir the chocolate until smooth, then add the sugar and golden syrup and heat for a further 5 minutes, stirring all the time, until thick and glossy. set aside until needed.
To make the topping, whip the cream with the vanilla and sugar for 2 minutes, using an electric whisk, until it is soft and thick. Spoon the whipped cream over the meringue wreath in a thick layer until evenly covered. Then arrange the raspberries on top of the cream around the wreath.
Just before serving, reheat the chocolate sauce until just warm. drizzle over the wreath with a spoon, then dust with a little icing sugar.
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