Pour the chicken stock and pork steaks into an ovenproof dish and cook in the preheated oven until no longer pink in the centre, 45 minutes to 1 hour.
Cut the carrots, swede and parsnips into small cubes or sticks. Put them in another ovenproof dish with the oil and sage. Place them in the oven next to the meat and bake until tender, about 45 minutes, turning them half way through.
Ten minutes before the pork comes out, fry the onion and mushrooms in oil or butter in a large frying pan till browned and soft.
Add the sherry and let it cook over medium heat till evaporated, about 5 minutes.
Take 5 tablespoon from the chicken stock in the dish with the pork and add them to the pan. Let reduce by half, stirring to stop the sauce from burning. Add 2 more tablespoons of the stock and stir in the creme fraiche.
Next add the paprika, black pepper and a pinch of salt. Dilute the cornflour with about 1 tablespoon hot water and add it to the sauce. Cook stirring till thickened. Add the pork steaks with 2 tablespoons of the stock. Cook for 2 to 3 minutes until heated through, stirring occasionally. Remove the roasted vegetables from the oven and serve with the meat.