Chocolate and Orange Trifle

This is based on a recipe from Food and Drink 2000.  A delicious and elegant dessert.

1 chocolate cake
2 oranges
1/2 cup Grand Marnier
1 1/2 cups whipping cream
8 oz white chocolate

1. Slice cake 3/4 inch thick.  Line a bowl (glass preferably) with the cake.  Peel oranges and remove pith.  Place orange sections over cake.  Pour Grand Marnier over cake and oranges.  Cover and leave to soak for 1 hour.
2. Bring cream to boil.  Remove from heat and stir in chocolate until melted.  Transfer to a bowl and leave to set in refrigerator for 3 hours or until it holds its shape.  Remove from refrigerator and whisk until thick and the whisk holds a soft peak.  Spoon onto oranges, completely covering them.