I made this recently as my contribution to a 'get together' lunch. It used up a bar of chocolate I would probably have eaten! It's a recipe I've made many times and is adapted from an old American baking book I picked up on one of my visits. Have mentioned it on here before - 'Favorite Cakes and Tarts my Mom made'.
For the dough you need - 114g cold butter cut into pieces, 150g caster sugar, 1 large egg and 1 egg white, 300g plain flour, 40g cocoa and 1 tspn baking powder
For the filling - 250g dark chocolate, chopped [not more than 60%], 90g cubed butter, 2 large beaten eggs, 85ml double cream, 50g caster sugar and 1 tspn vanilla extract
Preheat oven 190C/Gas5 20cm tart tin
Cream butter and sugar together till soft. Beat in the egg and egg white. Sieve the flour, cocoa and baking powder together then add to the mixture and fold in. Bring together into a disc, wrap in cling film and put in fridge for 30 mins. Roll out between 2 layers of parchment paper or clingfilm then line tart tin. Cover with parchment paper and baking beans and bake blind for 20 mins.
Melt the chocolate and butter over a low heat. Cool. Add the rest of the filling ingredients and pour into the tin. Bake for 20 mins till filling is set but still a bit wobbly in the middle.
The tart is quite rich, so you only need a small slice! The pastry is quite cakey, but is still a good contrast in texture to the soft filling. Nice served with vanilla ice cream.