Score the lamb shoulder.Rub lamb with olive oil, oregano, garlic,salt and pepper. Massage well into lamb.
Place half the oil in a large, heavy based frying pan over a moderately high heat. Add celery carrot and onion, sauté for 5-8 minutes, stirring occasionally or until soft and golden. Remove and place in a deep half gastronome. Return pan to the heat and add remaining oil. Add lamb and brown all over.
Remove lamb and nestle on top of mirepoix. Add stock, cover with baking paper and foil. Place in combi oven at 94°C for 10 hours or 160°C for 4 hours. Remove Lamb from gastronome. Pull lamb off the bone and shred.
Spread warm pita with Tzatziki and or Taramasalata, followed by red onion, roast capsicum, parsley, tomatoes, salad leaves and a generous serving of lamb. Add crispy hot chips and wrap the pita around fillings and serve.