Well cooled goose liver cut into slices at least 1 cm thick. Wash apples, quarter, core, cut into thin moon-shaped slices, sprinkle with lemon juice and set aside.preheat the oven to 200 °C. Melt butter or goose fat in a pan and sear the slices of goose liver for about 1/2 minute on each side. Lift the goose liver out of the pan, place in an ovenproof dish and cook in the preheated oven for 4 to 5 minutes. Meanwhile, pour off fat from pan, deglaze roasting stock with broth or sweet wine and soup and simmer apple slices in it over medium heat until sauce reduces and becomes creamy. Remove foie gras from oven and return to pan without the fat that has now formed in the pan. Allow to simmer under the apple slices for about 1 minute, add salt and pepper and serve hot with brown bread toasts.