Season the trout. Julienne the ham, pick and finely chop the parsley leaves, then place half into the trout cavities.
Carefully roll the trout in flour.
Over a medium heat, melt the butter and oil in a frying pan that fits both fish. Fry the trout for 5 minutes on each side, or until cooked and golden on the outside.
Add the cider and cook for 2 minutes, till bubbling and reducing.
Scatter over remaining ham and parsley. Place on plates and drizzle with sauce left in the pan to serve.