Preheat oven to 170°C/335°F (standard) or 150°C (fan).
Place garlic, onion and rosemary in a metal roasting pan.
Place lamb leg right side up in the pan. (Note 2).
Sprinkle generously with salt and pepper and rub it inches.
Turn lamb over and place it so it mostly sits on the garlic and onion. Sprinkle with more salt and pepper, rub it inches (Video helpful here).
Drizzle lamb with olive oil. Pour broth and water around the lamb – it won’t cover it, that’s ok, the lamb sinks into it. Cover with foil (don’t use a lid, you want a bit of liquid to steam out).
Place in the oven and roast for 4.5 hours. (See Notes for roasting time table).
Remove from the oven, remove foil. Turn lamb over. Check it to ensure the meat is tender (pry a bit off with a fork). If not, return, covered, to oven.
Return uncovered lamb to oven for a further 45 minutes or until well browned.
Remove lamb, spoon over pan juices generously. Transfer to serving platter, cover loosely with foil while you make the gravy (stays warm for 1 – 1.5 hours).
Use a large spoon to skim off some of the fat from the surface of the liquid.
Place pan on the stove on medium high. When the liquid bubbles, add flour.
Use a whisk to mix it in – this may take a few minutes as the liquid reduces.
Once it looks like sludge (see video), whisk in 1/2 – 1 cup of water until it becomes a gravy consistency to your taste. Adjust salt and pepper to taste – I rarely add extra salt.
Strain gravy into a bowl, pressing juices out of the onion etc.
Pour gravy into jug.
1. LAMB CUT: This recipe can be made with a leg or shoulder of lamb. Shoulder has more fat running through it than leg, so you can actually roast it uncovered (here’s my Slow Roasted Lamb Shoulder recipe), but this recipe will also work with shoulder. This recipe is designed for lamb leg because it’s leaner, so it benefits greatly from slow roasting partially submerged in liquid so it doesn’t dry out. Cooking it this way also infuses it with flavour.
2. The upper side of the lamb leg has more meat so we want to roast that partially submerged in the liquid for most of the cooking time. The upper side of the lamb is rounder and usually has more fat. The underside has less fat and is more flat.
3. TRY THIS WITH Truly Crunchy Roast Potatoes!
4. MORE ROAST LAMB: Ultra Tender Slow Cooker Roast Lamb, Slow Roasted Lamb Shoulder, Classic Roast Lamb with Gravy (i.e. it’s blushing pink inside) and Slow Roasted GREEK Leg of Lamb (delish lemon garlic flavours!).
5. Roasting Times (this cook method is pretty forgiving so round up to determine cook time e.g. if your lamb is 1.8kg, use the 2 kg cook times).