For a small fillet to serve 2, purchase the top of the fillet, which weighs 400-500g, and ask the butcher to remove the fine sinew if it is still attached. Preheat the oven to 200°C, placing a small roasting tin with a rack inside it while it heats. Season the beef with salt and pepper before sealing in very hot clarified butter or olive oil in a frying pan, then transfer to the roasting tin and cook for 10 minutes. Still on its rack, transfer the roast fillet to a plate [to collect any juices], cover loosely with foil and leave to rest for 10 minutes at room temperature. The meat should be very pink and juicy.