Line a baking sheet with nonstick baking paper. Coarsely grind the hazelnuts in a food processor (or chop them and then crush with a pestle and mortar), then set them aside.
Whisk the egg whites in a large bowl until they form soft peaks. Gradually add the sugar, a teaspoon at a time, whisking until the mixture is very stiff and shiny. The mixture should stay put, even when the bowl is tilted. Fold in the vinegar and vanilla extract, then fold in the ground nuts.
Spoon the meringue mixture on to the lined baking sheet, to make approximately 25 mini meringues, spacing them apart as they will expand slightly in the oven. Bake in a preheated oven, 110°C (225°F), Gas Mark ¼, for 45 –60 minutes or until the meringues are firm and may be easily peeled off the paper.
Allow to cool on the baking sheet. Serve the cooled meringues topped with a little crème fraîche and a small sprig of redcurrants.