The mango mousse recipe is not from "Bittersweet" -- I was borrowing a technique of "stacking" contrasting mousses from that book.  I grabbed the mango mousse recipe off Recipezaar -- it was gelatin, mango puree, sugar, lemon juice, and heavy cream.  As I noted above, I used fresh mangos for the puree.  I'll be really interested in your results.  Are you going to boil the puree as Chiantiglacee suggests?