Set pressure cooker to the “Saute/Sear” HIGH TEMP. Wait a minute or 2 for it to heat up.
Add two of the shanks and brown them off. When the shanks have developed a nice brown caramel colour, remove them and put the other two shanks in and repeat. Brown off as much as you can before starting the pressure cooking proper. (Keep the lid off during this process) [See note 1]
Place all 4 shanks aside on a plate covered. Add the onion, celery and carrots to the inner pot and cook for 3 minutes.
Add the tomato paste, stir through and cook for a further 3 minutes.
Add the red wine and beef stock/broth and stir through, followed by the whole garlic cloves and rosemary sprigs placed on top.
Add the lamb shanks back into the pot, nestling them into the mixture.
Secure and lock in lid in clockwise direction. Set the valve to seal.
Select the menu by pressing the PRESSURE COOK button
Select the “MEAT/POULTRY” setting and adjust timer to cook for 60 minutes.
Press start to commence the cooking process.
Once timer has gone off, release pressure valve so steam can escape.
Remove lid and take out the lamb shanks. Place aside into a baking tray.
Remove inner pot and use a sieve to strain the liquid from the vegetables into a saucepan. Disgard the vegetables. Heat the liquid on low heat for 5 minutes until it thickens just slightly and then remove from heat.
Potatoes: Add the peeled potatoes to a pot of hot water and bring to the boil. Cook for 10 to 12 minutes then test with a fork to see if soft. Once they are soft, drain the water and mash with a potato masher. Add the milk, butter and mayonnaise until smooth and creamy.
Beans: Steam the bean in a steamer over a pot of water for about 5 minutes, or cook in a bowl of water in the microwave for 3 minutes until just cooked.
Plating up: Evenly spread the mashed potato across 4 large plate, add a lamb shank to each and drizzle on a little of the sauce, and add the green beans.