This is a dessert I came up with in 2007 for our Christmas lunch at work.
We used it again for valentines 2008 it worked so well. Be aware it is a
very long post but it contains the recipes for each element of the dessert:
  #1 The chocolate tart with a choc-chip crust
  #2 A mocha-dark choclate truffle
  #3 Fudgy Chocolate brownies

Each of them can be made on their own obviously, but they work so well together
for special occasions
..

   Chocolate Tart
Makes 1 x 30cm tart

  pastry:
    100g dark chocolate
    125g butter (proper butter not margarine please)
    100g castor sugar
    250g cake flour
    2 egg yolks
    30ml water

  Filling
    300g dark chocolate
    250ml cream
    250ml milk
    100g butter
    3 egg yolks
    50g castor sugar

  Making the pastry
    Finely chop the chocolate,
    beat sugar and butter till smooth.
    add the flour and mix until its crumbly in texture
    add the yolks and mix til incorparated, if it forms a ball, its ready.
    if not, add enough of the water to form a soft dough, mix in the chocolate
    Chill for 30 minutes, wrapped in plastic
    Grease a loose bottom tart pan, line with the pastry
    Pierce with a fork all over the base and freeze for at least a hour.
    bake at 200C for 12 – 15 minutes, allow to cool

  Making the filling
    melt the choclate.
    bring cream, milk and butter to the boil
    whisk the yolks and castor sugar together
    whisking continuously, slowly add the hot liquids to the egg mixture,
    return to heat and cook, whisking vigourously until the custard is
    thick enough to coat the back of a spoon   
    Cool the custard for about 5 minutes before beating in the melted chocolate.
    (if it curdles, place in a ice bath and beat in a little cold milk)
    Allow to set in the fridge overnight

Chocolate Truffles
  Ingredients:
    500g dark chocolate
    6 egg yolks
    125g butter
    25ml rum (or brandy, whatever you have on hand)
    25ml ultrastrong espresso

  The how to do it:
    Melt the chocolate in  a double boiler
    Add the egg yolks and beat until incorporated.
    Add the butter in small pieces mixing it in.
    add the remaining ingredients add mix with a spoon
    until it binds together and becomes smooth
    Allow to cool in the fridge, before taking teaspoonfuls
    of the mixture and rolling them in ur hands to form small balls.
    Roll in cocoa powder and set aside

   
Brownies

Serving Size : 12
  Ingredients
    125g butter
    100g dark chocolate
    2 eggs — well beaten
    250ml cake flour
    2.5ml baking powder
    1ml salt
    5ml vanilla extract
    125ml walnuts — chopped (optional)
    500ml brown sugar

  How to make
    Melt butter and chocolate in double boiler. Cool slightly.
    Beat in remaining ingredients by hand. Pour into a greased
    20 x 30cm baking pan.
    Bake at 180C degrees until set, or about 30 minutes.