Clean, wash and drain the salad and pluck into bite-sized pieces. Peel and finely chop the onion. Mix vinegar, salt, pepper and onion, add oil. Wash the liver and pat dry.
Heat the fat in a frying pan and fry the turkey livers for approx. 5 minutes, turning them over. Season with salt and pepper and remove from the pan. Pluck the sage leaves from the stalk. Wrap a piece of liver in half a slice of Parma ham and place a sage leaf on top.
Turn again briefly in the hot frying fat. Deglaze with stock and sherry, bring to the boil and keep warm. For the mashed potatoes bring 1/2 litre of water with a little salt to the boil. Pour in cold milk and sprinkle the puree flakes.
Allow to swell for 1 minute, stir again. Refine with a little butter and nutmeg as desired. Pour vinaigrette over the salad and arrange everything on plates. Garnish with sage.