First, forget everything your Grandma told you about poking it to see if it’s done. She was wrong. You need a thermometer. It’s not cheating; it’s science with a beep. The perfect lamb roast lives and dies by a single, glorious number: 130°F to 135°F (that’s 54°C to 57°C for you metric boffins).
Pull it out of the oven at this temp, and you’re in medium-rare paradise. The inside will be a rosy, tender pink that makes vegetarians weep into their kale salads. Let it rest for 15 minutes—it will climb a few degrees—and you’ve nailed it. Anything above 145°F, and you’ve entered “mutton shoe territory.” Don’t be a hero.
