Preheat pressure cooker by pressing the saute button.

Add oil to the pot.

Add the lamb to the pot, making sure to not crowd the pan. You may have to work in batches.

Brown each piece of lamb on both sides, remove from pot and set aside.

Add the onion to the pot and saute 2 minutes, stirring to remove browned bits from the bottom of the pot.

Add the garlic, celery, carrots, turnip and leeks.

Saute 1 to 2 minutes.

Add the lamb back to the pot.

Pour in the beef stock.

Add the potatoes and thyme sprigs.

Stir well and season with salt and freshly ground black pepper to taste.

Place the lid on top and lock into place.

Turn the steam release valve to closed.

Press the keep warm/cancel button to reset the unit.

Select the meat/stew and adjust the time to 20 minutes by pressing the minus button.

Allow the unit to come to pressure and count down.

Once the timer has finished counting down, allow the unit to naturally release the steam.

When the steam has released completely on it's own, remove the lid.

Remove the thyme stems and discard.

Stir in the freshly chopped parsley and adjust salt and pepper to taste.