Lamb Leg Sirloin Half is the top half of a hind leg of lamb.It contains tender meat, and may be sold bone-in or boneless. It has more fat than the lower half of the leg, but also more meat.
Bone-in, it may be sold whole, or cut into chops.
The boneless can be rolled or tied, or used flat as a butterflied leg of lamb.
Bone-in, it will weigh 3 to 4 pounds (1.4 to 1.8 kg); boneless, it will weigh about 2 pounds (about 1 kg.)
Boned or boneless, 1 will feed about 4 people.
Roast at 160 C (325 F). Allow:
25 minutes per 500 g / pound for rare (final internal temperature of 63 C / 145 F);
30 minutes per 500 g / pound for medium (final internal temperature of 71 C / 160 F);
34 minutes per 500 g / pound for well-done (final internal temperature of 75 C / 170 F).
Remove the meat from the oven when the internal temperature reads a few degrees below the temperature you are aiming for. Cover with foil and let stand about 10 to 20 minutes; the juices will be drawn back into the meat and it will finish cooking the final few degrees from the residual heat.
When butterflied, cook by broiling (aka grilling in the UK) or grilling (aka BBQ outside the US.)
LAMB Cooking Times and Temperatures. Ontario Lamb site. Accessed June 2016 at .http://www.lambrecipes.ca/CulinaryIndustry/TimeTemperatureChart.aspx