Heat the oil in a nonstick frying pan until smoking hot. Add the steaks and cook over a very high heat for about 2 minutes on each side, if you want your steaks to be medium rare. Remove to a plate, season with salt and pepper and keep warm in a low oven.
Pour the vinegar, wine and stock into the pan and boil for 30 seconds, scraping any sediment from the base of the pan. Add the garlic and fennel seeds and whisk in the sun-dried tomato purée and crushed chillies. Bring the sauce to the boil and boil fast to reduce until syrupy.
Transfer the steaks to warmed serving plates, pouring any collected meat juices into the sauce. Return the sauce to the boil, then season with salt and pepper.
Pour the sauce over the steaks and serve immediately, garnished with chopped parsley and wild rocket leaves, if liked. Slice the steaks before serving, if you wish.