Preheat the oven to 200C/400F/Gas 6.
For the beef, place all of the ingredients into a small bowl and leave the beef to marinate for about ten minutes.
Heat the griddle pan over a high heat and griddle the marinated beef for 3-4 minutes. Turn the beef over and cook on the other side for 2-3 minutes. Set aside and leave to rest in a warm place.
For the fondant, heat the oil in an ovenproof frying pan, add the swede and cook for 2-3 minutes on each side, until golden-brown. Add the chicken stock to cover the swede.
Transfer the pan to the oven and bake for 12-14 minutes, or until softened.
To serve, place the marinated griddled beef onto a serving plate along with the swede fondant.