Cut tomatoes in halves; take out some of the pulp. Fry 1 large onion in butter, add the tomato pulp, a piece of beef-marrow, 2 sprigs of chopped parsley, salt and pepper. Remove from the fire; add a beaten egg and mix with bread-crumbs and a pinch of nutmeg. Then fill the tomatoes, sprinkle with buttered bread-crumbs and bake until done. Serve on a platter with poached eggs. Garnish with croutons.