Make the pastry and line a loose-bottomed 28cm/11 inch flan tin
Bake blind and allow to cool
Roll the extra pastry out to the same thickness in a long rectangular shape, dusting as you go, and divide into 14 strips 2
5 cm/1 inch wide
Set these aside - you will need them to finish off the tart
Turn the oven down to 170?C/325?F/gas 3
Whip together the ricotta, mascarpone, icing sugar, orange zest, vanilla seeds and egg yolks until smooth and shiny
In a separate bowl whip up your egg whites until stiff - you can test if they\'re done by holding the bowl upside down over your head
Obviously the mixture should stick to the bowl and not fall on your head! Gently fold the egg whites into the mixture
Pour into your cooled tart mould and sprinkle the chocolate over the top
Lay 7 strips of pastry across the tart, equally spaced, and then place the other 7 the other way on top of them like a lattice
Use your thumbs to trim any excess pastry off the side of the mould - this will stick it to the pastry below
Brush the pastry with a little of the beaten egg and then dust with a little icing sugar
Bake in the preheated oven for 40-45 minutes