I made a first-round attempt at this on the weekend, and the following represents the conclusions my partner (who is more accustomed to roasting pork than I) and I came to about getting it right next time. The base recipe I was working from was this one, from the promotional food magazine in the grocery store, but I added the walnuts and assorted other bits and bobs.

( Dietary and other notes )

( What you need )

( What you do with it )

I served this with a side of kale sautéed with bacon, because in for a pig in for a... bacon?

Adapted from In the Kitchen by Campion and Curtis

( Dietary and accessibility notes )

You need:

A portion of lamb leg suitable for roasting. 1kg to 1.5kg, say?
About 12 cloves of garlic
2-4 tablespoons of pesto
Possibly salt and pepper to season?

What you should do:

- peel the garlic cloves
- cut vertical slashes all over the lamb, and tuck the garlic in
- slather the entire thing in pesto.

For best results, leave this all to marinade for a few hours. You might want to season with salt and pepper, but I didn't bother. Then roast! I recommend 180 degrees celcius, about 25 minutes per 500 grams of lamb. You're aiming for medium-rare. Test by sticking a butter knife into the lamb. If it comes out cold, cook another 5 minutes or so. You want the knife surface to be tepid/skin temperature warm - about the same temperature as you'd heat baby's milk to, if that helps.