1: Pre-heat the oven to 150C / Gas mark 2.
2: Firstly prepare the lamb. Place on a chopping board and using a sharp knife, score the lamb shoulder all over by slashing the skin, making sure you don’t go too deep into the flesh. Set aside while you prepare the rub.
3: Warm a small frying pan over a medium heat and add the fennel seeds, peppercorns and sea salt. Heat for 2-3 minutes, shaking the pan from time to time until lightly toasted, fragrant and aromatic. Remove from the heat and transfer the spices to a pestle and mortar and allow to cool. Bash together until they are finely ground.
4: Brush the Dijon mustard all over the surface of the lamb, on both sides so it’s evenly and generously coated. Sprinkle the fennel seed mix on top of this, rubbing and patting it into the mustard coating with your hands.
5: Place the fennel and onion quarters into a large roasting tray, so they cover the base. Sit the lamb comfortably on top and drizzle with the olive oil. Roast in the pre-heated oven for 4-5 hours, basting from time to time until the meat is completely tender and falling off from the bone. It should easily flake into pieces for serving.
6: Remove the lamb from the oven and lift out of the tin onto a board or tray. Cover with tin foil and allow to rest.
7: While the lamb is resting prepare the fennel salsa. Remove the fennel and onion from the roasting tray and place onto a chopping board. Roughly chop them to a ‘salsa’ type consistency and place into a medium mixing bowl. Add the vinegar, chillies and chopped dill and mint. Give it a good stir and season to taste with salt and pepper.
8: Place the roasting tray with all the lovely lamb juices over a high heat. Once the juices start to bubble away, pour in the lamb stock and de-glaze the pan. Reduce down for around 5-10 minutes until thickened, whisking frequently. Strain through a sieve before serving.
9: Transfer the lamb to a serving board or platter and serve it whole or flaked into pieces. Serve the fennel ‘salsa’ alongside with the reduced sauce. Goes brilliantly well with a potato salad or pitta breads.