Preheat oven to 150 degrees fan forced.
In your baking tray add in all your ingredients except for the lamb and bring together with your fingers until you have a bright green marinade.
Place your lamb shoulder and rub it in until it's covered in the marinade.
Add 200ml water to the bottom of the tray, cover in foil and place in oven.
Cook for 2 hours at 150 degrees.
Then cook for 3 and a half hours at 130 degrees.
Then remove foil and cook uncovered for 30 more minutes at 130 degrees Celsius.
Base your lamb shoulder each hour with the pan juices.
Remove from oven when done and allow to rest.
In a very hot grill heated oven, blacken your onion, jalapeño, green chilli and green pepper until deeply charred.
Allow to steam covered in a bowl and then peel the blackened skins off.
Add into a blender with the rest of the ingredients, eye ball a glug of EVOO and add more if needed.
Season with salt to taste.