I love a chocolate tart and it will often be my first choice off the menu. They can be extremely rich though and not something you can eat much of. This one, however, has all the chocolatey depth and richness but at the same time it's as light as a feather and is, in my humble opinion, pretty close to perfection.
No it's not a super simple recipe but with a bit of patience it shouldn't cause you too many problems. Adding the egg yolk to the pastry makes it very easy to work with and the tip below about using leftover scraps to fill any cracks is worth remembering. The filling is also pretty easy as long as you're prepared to be a little patient when whisking up the eggs.
In short, this is a dinner party classic and any effort put in is more than rewarded at the other end.
Chocolate Mousse Tart
(from Simon Hopkinson's Roast Chicken & Other Stories but also published in Books for Cooks Favourite Recipes from Books 1, 2 & 3)
for the pastry case
175g/6oz plain flour
45g/1 1/2oz sifted icing sugar
a good pinch of salt
90g/30z very cold butter, cubed
1 organic egg yolk plus 1 tbsp cold water
for the filling
200g/7oz plain chocolate, broken into pieces
3 organic egg yolks
2 organic eggs
3 tbsp caster sugar
1) Lightly butter a 24cm/9 1/2inch tart tin and put it into the fridge to chill.
2) Put the flour, icing sugar and salt in a food processor and pulse a couple of times to aerate. Add the butter and process until the mixture resembles fine breadcrumbs. Add the yolk and water (if necessary) and process until the pastry just draws together. Turn out onto a floured work surface and knead briefly to form a flat round.
3) Unless it's a very hot day you can roll the pastry out straightaway without chilling it first. Line the chilled tin, trim the pastry (although leave a centimetre or two above the rim as it will shrink - you can trim it some more later) and put into the fridge to rest for at least an hour (I left mine overnight with no adverse effects). Do not through any leftover pastry away, but wrap it in some cling film for later (see below).
4) Put a baking sheet in the oven and preheat to 190c/375f). Line the chilled pastry case with baking parchment, fill with baking beans and cook for 10 minutes. Carefully remove the beans and paper and cook for another 10 minutes or until the pastry is a light biscuit brown. Any cracks can be filled with your spare pastry - the residual heat will cook it.
5) For the filling, melt the butter and chocolate together either in a microwave or in a bowl over a pan of barely simmering water. Leave to cool slightly.
6) Whisk the egg yolks, eggs and sugar until very thick and pale (this is the key to this dish - using a hand mixer I did this for at least 10 minutes). Pour the melted chocolate mixture on to the egg mixture and fold together until well mixed.
7) Pour into the pastry case and bake in the oven for 8 minutes when the tart filling will look just set but still a little wobbly. Leave to cool completely before trying to cut it. Finish with a dusting of icing sugar and serve with fromage frais, creme fraiche, cream or ice cream.