Place the tallow, garlic, onion, rosemary and celery in the base of your pressure cooker. Saute over medium heat for 5 minutes.

Add the salt, pepper, red wine vinegar and tomato puree. Continue cooking for another 5 minutes.

Add the beef stock and stir well.

Gently place the lamb shoulder into the pot, ensuring that it is just covered by the liquid. Add extra beef stock or water until the lamb is covered.

Bring to a boil and secure the lid onto the pressure cooker. Turn the dial to the highest pressure setting and allow to pressurize.

Once your cooker starts to release steam, drop the heat to low and leave to cook for 2 hours or 30 minutes per pound.

After 2 hours, turn off the heat and leave to release pressure for 20 minutes.

After 20 minutes, turn to dial to release any remaining steam. If there is a big release of steam, leave the pressure cooker for another 5 minutes before attempting to open.

Remove the lid of the pressure cooker and gently remove the piece of lamb shoulder. We recommend using a spider tool or 2 sets of tongs.

Turn the pressure cooker back onto medium heat and allow to liquid to simmer and reduce by ¼.

While the liquid is reducing, use tongs to pull the lamb meat off the bone and roughly chop into bite sized chunks.

Add the chopped lamb meat back into the pressure cooker, along with the mushrooms and simmer for 10 minutes.

Serve topped with 2 tablespoons of Sour Cream and 1 tablespoon of grated Parmesan Cheese and enjoy!