Method 
1. Pre-heat an oven to 115°C and another to 220°C. Line a 2-3cm deep, shallow baking tray with cling wrap.
2. De-bone the saddle of lamb, remove the loins and trim lengthways about 1cm (if the loin is wide and flat). Trim any fat. Roast the lamb bones and trimmings in the oven at 220°C until brown. Drain any fat and discard. Place the bones in a pan with the veal stock and leek tops and simmer gently for 45 minutes, skimming regularly. Pass through a fine sieve and reserve.
3. For the black pudding, quickly blanch the pork fat in boiling water and sweat the onion in a frying pan and cool. Strain the blood through muslin to remove any ‘strings’. Mix all dry ingredients in a bowl, including flour and oatmeal until well combined, making sure there are no lumps. Mix blanched fat, onions and barley into the dry ingredients until well combined. Stir strained blood into the mixture, until smooth. Pour mixture in the prepared tray and cook in a water bath, in the oven at 115°C for 30-40 minutes. Set aside to cool.
4. For the Leek “Boulangere”, gently heat the butter in a deep frying pan. Add the chopped leeks and sweat until soft. Stir through parsley. Season with sea salt and freshly ground pepper, and then drain on a cloth. Slice the potatoes to 2mm thick. Line the potatoes, overlapping, in a shallow oven-proof tray, about 12cm wide and 20cm long. Season the layer of potatoes, and then spread with the leeks. Ladle over some of the lamb gravy, and repeat this process until it is 3cm deep. Reserve the remaining gravy.
5. Cover the dish with baking paper and aluminium foil and cook in the oven set at 220°C, for approximately 35 minutes or until the potato is cooked through. Place a baking tray with a weight on top of the potatoes to flatten Boulangere. Set aside to cool in a fridge until firm. Cut into rounds using pastry cutters.
6. To make the chicken mousse, mince the chicken in a food processor with a little sea salt and freshly ground pepper. Slowly add the egg whites and then the chilled cream to form a smooth mousse, scraping the sides down regularly. Pass the chicken mousse through a fine sieve to remove any sinew. Set aside in the fridge.
7. Heat a frying pan over high heat and add about 1 tablespoon of oil. Season the lamb loins with salt and pepper, and sear very quickly in the pan. Place in the fridge to cool. Trim the ends from the loins and cut each into half.
8. In a food processor, add 500g of chopped black pudding and 3 tablespoons of the chicken mousse and pulse until well combined. Lay a large piece of cling wrap on a board. Lay a square piece of caul fat (large enough to wrap the lamb) on top of the cling wrap and spoon about 2-3 tablespoons in the centre. Lay a piece of baking paper on top and gently roll out the mousse until about 2-3mm thick. Place the chilled lamb at the nearest edge of the black pudding and roll to wrap the lamb completely in the caul, using it to cover the lamb evenly with the mousse. Trim the caul with scissors to make a neat parcel. Wrap tightly in cling wrap and tie knots at each end.
9. To set the black pudding mousse, place wrapped lamb roll into a steamer for 3 minutes. Heat an oven-proof frying pan over medium heat. Unwrap the rolls and seal in the frying pan. Place in the oven at 220°C for 5 minutes for rare. Rest the meat before carving into pieces.
10. For the date puree heat a frying pan and cook the dates with the chicken stock, until very soft. Once the dates are cooked, puree until smooth in a blender. Season with salt, pepper, 10g of the butter and add a little lemon juice. Pass through a fine sieve and set aside.
11. For the buttered baby leeks, blanch the baby leeks in a large saucepan of boiling salted water. Refresh in iced water.
12. To serve, reheat portions of the Boulangere in the cooler oven. Heat the puree and place a small spoonful into the centre of each plate. Reheat the leeks and then toss in remaining butter and season. Place the baby leeks onto the plate. Place a piece of the potato to the side of the leeks. Carve the rested lamb into 3 pieces. Season the cut meat with sea salt flakes and place each piece on top of 2 pieces of baby leek. Heat the remaining gravy, add a squeeze of lemon juice. Stir through parsley and spoon a little gravy onto the plate.
