I got these hollow truffle shells from a cake decorating supply store. The tray is very flimsy so be careful when picking it up!Using a plain bittersweet chocolate ganache as a base, I added a small tin of sweetened chestnut purée. Let the filling cool until it is pipeable, then fill the shells completely. Leave a bit of space at the top for sealing.After a night in the fridge, the centres were completely set. Temper some bittersweet chocolate, then pipe a small amount to seal the shells.After the seal has set, use a chocolate dipping fork to coat the truffle shells with tempered chocolate. Place them carefully on a sheet of parchment to harden.Sigh, still not getting a perfect temper. The chestnut flavour is too subtle to be detected. I would use milk chocolate couverture next time.