Like this? http://www.foodspotting.com/places/107610-marzano-s-restaurant-tacoma/items/135659-brandied-duck-sausage-lasagna
here's another... http://frommytable.com/2009/07/16/duck-lasagna-strapazatta/
and they talk about it here...
Some use a bechamel, some a ratatouille... I would shy away from too much tomato, let the duck and brie shine through. I was thinking maybe a cranberry sauce?
Completely OT, but wondering if you ever saw the reply to your request for an orange cake with pieces of orange? I was searching for something related and came upon that CH thread. Saw that the recipe was posted twice by the poster and wanted to make sure you had seen it!