(I have adapted this freely from the one in Green and Blacks Chocolate Book)

Pastry

175g (6oz.) Plain Flour
40g (1 ½ oz.) Caster Sugar
90g (3 oz.) Butter, chilled.
Grated Zest of 1 Orange (a Seville is perfect but ordinary will do)
3 Tablespoons Water

Filling
200g (2 oz.) Dark Chocolate (75% cocoa solids is perfect)
250ml (9oz.) Cream
5 Large Egg Yolks
90g (3 oz.) Caster Sugar
The Juice of the grated orange
3 Tablespoons Orange Liqueur (Cointreau or Grand Marnier, optional but nice)

Cut the butter into dice and process with the flour and orange zest in a food processor (or rub in by hand) until crumblike. Bind with the water and rest in a fridge for 30mts.

Roll out the pastry to line an 20cm ( 8”) tart tin.
Cover this with parchment and baking beans and bake blind at 190C,375F, Gas 5 for 20 mts.
Check this while cooking, if it starts to brown too much lower the temperature.
(In Fan Ovens it should be 175C.)

Take off the paper and continue cooking for a further 10 mins. until biscuit coloured.
Leave this too cool.

Break up the chocolate and put it with the cream in a bowl over a pot of barely simmering water. Stir occasionally until the chocolate melts.

Beat the egg yolks and the sugar together until light and thick.
Take the melted chocolate off the saucepan and stir in the egg mixture.

Now put this bowl back on the pot and stir over the simmering water until it thickens.

Now stir in the orange juice and the liqueur and then stir for another 4 minutes over the heat.
Pour this into the cooled pastry shell and chill for 3 hours to set.

This is so dark intense and delicious that you need only a small slice and serve it with whipped cream