Prepare the pastry by creaming the butter and sugar together in an electric mixer. Mix in the vanilla paste. Add the egg followed by the flour and mix until the dough starts coming together.
Tip the dough onto a clean work surface, press together into a disc and wrap in plastic wrap.
Refrigerate for 30 minutes.
Lightly grease a 25cm tart tin and place on a baking tray lined with baking paper.
Dust the work surface with a little icing sugar and roll the dough out into a rough circle. Carefully roll the dough around the rolling pin to help lift it over the tart tin.
Gently press the dough into the tin and patch up any cracked areas. Let the excess pastry hang over the edges, we'll neaten this up later.
Line the tart with a piece of baking paper and refrigerate for 20 minutes.
Preheat your oven to 200°C.
Prepare the filling by placing the Nutella and dark chocolate in a bowl.
Place the double cream and milk in a saucepan and bring to the boil, then remove from the heat and pour into the bowl. Whisk until you have a smooth mixture. Whisk in the eggs.
The mixture will be very runny.
Add baking beans to the lined tart dish and bake for 15 minutes. Remove the beans and the baking paper and bake for a further 5-10 minutes, or until the pastry is golden and cooked through.
Turn the oven temperature down to 160°C.
Melt some extra dark chocolate and brush over the warm pastry. Pour the filling into the tin and pop it back into the oven for 40 minutes.
The filling should be very wobbly when it comes out, but not liquid. Allow to cool completely.
Trim the excess pastry from the tart. Grab your extra block of chocolate and use a potato peeler to scrape out chocolate curls - this will be easier if the chocolate is at room temperature.
Pile the curls onto the cooled tart, then finish with a dusting of icing sugar. Recipe reprinted with permission of CupcakesandCouscous. To see more recipes, click here.