First, make the salt-crust dough. Mix the flour and salt together in a large bowl. Add the egg whites and 400ml water, and stir together with a wooden spoon to form a firm dough – add a little more water if needed. Tip the dough onto a lightly floured surface and knead for 10 mins or until smooth. Wrap in cling film and set aside to rest for 1 hr. (You can also make the dough in a freestanding mixer with a dough hook attachment).
Heat oven to 160C/140C fan/gas 3 and line a baking tray with parchment. Divide the dough into 4 even-sized pieces. On a lightly floured surface, roll each into a circle almost 1cm thick. Place a lamb shank in the centre of each disc of dough and tuck 2 garlic cloves underneath. Brush the edge of the dough with a little water, then gather it up and around the lamb shank, leaving the bone exposed. Make sure all the meat is covered and the pastry is well sealed. Transfer to the lined tray. Can be assembled 1 day ahead and chilled. Put the lamb in the oven and bake for 3 hrs 30 mins, by which time the crust will have turned a dark brown.
Once the lamb is cooked, leave it to rest for 30 mins. Using a bread knife, open the crust and very carefully remove the shanks and the softened garlic cloves, then discard the crust. Place the shanks on a baking tray and drizzle with a little oil. Blowtorch the lamb (see tip) to give it a crisp, toasty finish. Serve the lamb with the garlic cloves, Soused red cabbage and Beer-braised Puy lentils (see Goes well with for the recipes).
At your butcher'sGet your butcher to French-trim the shanks, but remember to ask them to keep the trimmings, as it’s delicious added to the braised lentils. If they ask what you mean by French-trim, say you want the shank bone exposed and scraped clean, with only the main ‘ball’ of meat attached.
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Creating a salt-crustAs well as lamb, salt-baking is a great way of cooking root vegetables.
The key to blow-torchingI like blowtorching savoury food before serving, but the technique is often misunderstood. The key is to create a charred finish. What you want to achieve is a thin ‘scorched’ layer of treacly flavour on the food, which is nothing like the bitter flavour you get from burning something in a pan. If you don’t have a blowtorch, the shanks can be finished off under a hot grill.