Peel and seed the grapes. Set aside. Place the flour in a shallow bowl, the eggs in another shallow bowl, and the bread crumbs on a baking sheet. Dip the rabbit livers first in the flour, then in the beaten egg, and lastly in the bread crumbs. Heat half the butter in a frying pan and brown the livers on both sides. If the butter burns, discard it, and add fresh butter. Season the liver with Four Spices and coarse salt. Transfer the liver to a warmed serving platter and keep warm. Drain all the fat from the frying pan and add the raspberry vinegar. Cook over a low heat, scraping the bottom of the pan with a wooden spoon to dislodge any attached meat particles. Reduce the vinegar by 1/3. Whisk in the remaining butter and swirl the pan off the heat until it melts. Add the grapes to the sauce to serve, pour the sauce over the livers and serve very hot.
