I just did two ducks the traditional way. Confit the legs, used the skin for cracklings, duck stock, sous vide breast, rendered the fat, made a duck liver mousse. The only thing I didn't do was stuff the necks.
I used frozen. 1.5qt of liquid, 1c flour, 1c butter, and 1/4lb frozen okra. I just tossed it in there and felt I could gamble a bit with the amount. I felt it was just right, but who is to say I make my roux the same way you make your roux?
So seriously, that mascarpone is likely breaking when you mix it in with the ganache. You might not realize it because the ganache is keeping everything together. Room temperature ganache is pretty tight so I'm assuming you're using the beater? Try adding stabilizer twice. Once when you are mixing the mascarpone with the sugar, next when you're mixing the mascarpone with the ganache.
It seems as if I needed to add a lot of file to get the effect. I recall the previous batch I added the file about 30 minutes from the end. And yes, that's jasmine rice.
Uh, what kind of rice is normally served?