Place half the rosemary under the lamb and the other half in top - be generous with the amount you put
Slice 5 of the garlic heads in half and scatter around the lamb
Drizzle the lamb and garlic with Olive oil
Cover the tray with tin foil, tightly and place in the oven for 5 hours
About 45 minutes before the meat is ready, take the last garlic head and peel out the cloves. In a saucepan, combine the milk, cream and garlic over medium to low heat and let it infuse for a bit until the garlic is soft and the mixture is a little thick. Usually 20 - 25 minutes
Off the heat whisk in the cornstarch and about 80ml of the juices from the roast lamb, try to avoid the fat. Add Salt and while still whisking and return to the heat
Simmer until the sauce reaches your deired consistency, usually less than 5 minutes. If too watery you can add more cornstarch
Strain the sauce through a sieve
The meat should rest for about 15 - 20 minutes. It should pull apart easily. Serve with the sauce and enjoy!
Notes
You can also add mushrooms to the sauce. Before adding the cream just fry the mushrooms for a few minutes then continue with the recipes instructions. At the end, you don't need to strain the sauce.