Melt the butter and lard in a saucepan or casserole and, when hot, put in the pork, well rubbed over with salt. Cook to a nice brown colour, turning it so that it is equally browned on all sides. Then add the sliced onions, tomatoes, carrots, a little parsley and either the white wine or stock to moisten. Season highly with salt and pepper and simmer gently for 2 to 2½ hours till the meat is tender. Place the loin on a hot dish, strain the sauce over it and garnish with cooked vegetables, such as aubergines, pimientos, carrots, peas, small potatoes, sautés in a little butter.