Turn the heat down and add the butter and rosemary. Baste the rack with the butter.
Place in the oven and cook for 8 minutes for medium rare. Take out of the oven and baste again with the juices. Cover with foil and leave to rest for 5 minutes before carving.
GARDEN GREENS
200g spring greens or curly kale Knob of butter Salt & pepper
Blanch the greens for 4-5 minutes in salted boiling water. Drain and season with butter and salt & pepper.