2 kilogram leg of lamb, French trimmed
1 tablespoon finely chopped rosemary
2 cloves garlic, crushed
1 tablespoon Dijon mustard
4 cups plain flour
1½ cups fine sea salt
1 tablespoon ground fennel seed
1 tablespoon freshly ground pepper
2 egg whites, lightly beaten
1 cup water
1 egg yolk mixed with a little cold water
extra rosemary leaves
Preheat the oven to 180˚C.
Lamb: Combine the rosemary, garlic and mustard in a small bowl. Cut 6 deep slits in the lamb and push in half the herb paste. Rub the rest of the paste over both sides of the lamb. If you have a large flat grill plate, the lamb can be browned and cooled before rubbing with the mustard mixture. This doesn’t change the flavour, but does make the lamb look more attractive when the crust is broken.
Salt dough: Put the flour, salt, fennel and pepper in a food processor and pulse to combine. With the motor running add the combined egg whites and water to make dough, adding a little more water if necessary to bring the dough together. Tip onto a lightly floured the bench and knead for 1 minute.
Roll the dough out to a large 40 cm x 45 cm rectangle.
Place the lamb on the dough, presentation side down, and bring the sides of the dough up over the lamb, leaving the bone exposed. Wet the edges of the pastry and press firmly to seal. Turn the lamb right side up and place on a lined baking tray, making sure the dough around the bone is sealed tightly. Wet the pastry where necessary and smooth with your fingers to seal any cracks.
Brush the dough with egg wash and scatter over the rosemary leaves. Roast for 1½ hours then remove from the oven and rest the lamb for 15 minutes.
To serve: Carefully crack the crust open and, using a large fork, lift the lamb onto a serving plate. Serve with the mint aioli.