A delicious way to cook a butterflied leg of lamb boulangere style
Mix the thyme, salt and pepper with the olive oil
Put the leg of lamb into a large ziplock bag or tupperware container
Pour over the marinade
Put in the fridge to marinate for at least 24 and up to 48 hours
Peel the potatoes, onions and garlic
Using a sharp knife or mandolin slice the potatoes and onions as thinly as possible
If you are not cooking immediately, you can blanch the potatoes in boiling water to help keep them from going brown. Once blanched for a minute, drain and cool in a bowl of iced water, before covering. Drain and pat dry with a clean tea towel before using
Pre-heat the oven to 180C (175C fan oven)
Butter a roasting pan
Crush or finely chop the garlic and pick the thyme leaves
Put layers of potatoes, garlic, thyme and onions in the pan, seasoning with salt and pepper as you go
Pour over the stock - it should come about 2/3rds of the way up the potato mix
Cover the pan with foil and put in the oven for 10 minutes
Heat a large frying pan and sear the lamb on both sides till the fat starts to brown a little
Take the potato mixture out of the oven, remove the foil and put the lamb on top of the mixture. Reserve the foil for later!
Put it back in the oven at 180C (175C fan) for around an hour, till the lamb is cooked through. Check once or twice while the mix is cooking and if the potatoes are starting to dry out too much, you can add more stock and/or cover the dish with foil.
A meat thermometer reading of 62C will give you medium-rare lamb, 65 C for medium and 70 for well-done. At this stage your potatoes should be meltingly soft.
Take the pan out of the oven, cover with foil and allow to rest for at least 15 minutes and up to half an hour