Place the chestnuts, chopped apple and sausagemeat in a food processor, season and blitz together until smooth. Core the other apples, keeping the core. Cut off most of it, keeping 2cm from the base. Reinsert this back into the base of the apple, then, using a small spoon, fill the cavity with stuffing. Repeat with the other apples and make a horizontal slit all the way around each one.