Preheat the oven to 180˚C and grease 6 loose-bottomed tart cases (12 cm) with butter.

Melt the butter in a saucepan and add the cocoa powder, stirring well to combine. Crush the biscuits very finely in a food processor and add the melted butter. Line the base and sides of the tart cases with the crumb mixture and place in the fridge to set for about 30 minutes.

Meanwhile, beat the whole eggs in an electric mixer with a third of the sugar and the Vanilla Extract. Beat until the eggs double in volume and go white in colour. Place the rest of the sugar and the water in a saucepan and stir until the sugar dissolves and becomes syrupy. Place the chocolate and butter in the hot sugar mixture and stir until the chocolate dissolves. Allow to cool slightly before slowly folding the chocolate mixture into the whipped eggs until completely incorporated.

Remove the tart bases from the fridge, place on a baking tray and fill with the chocolate mixture all the way to the top. Bake in the pre-heated oven for 20 minutes or until just set. Remove from the oven and allow to cool completely before removing them from the tart bases.

To make the meringue, place the egg whites in a very clean electric mixer and whisk until soft peak stage. Slowly add the sugar 1 tbsp at a time, until the mixture is very thick, glossy and has very stiff peaks.

Using a spatula, swirl peaks of meringue on top of the chocolate bases. Sprinkle with some chopped hazelnuts and place back in the oven for 5 minutes or until the meringue is lightly golden.