For the lamb shanks, season and oil them all over and sear them in a Retigo combi oven set on hot air mode 220°C for 2 minutes using enamelled GN container 100 mm. Take the lamb shanks out of the GN container. Add the oil onions, celery and carrots to the GN container. Reduce the temperature to 190°C and cook for 6 minutes, adding the garlic for the last minute. Add the wine and cook it down for a minute. Now add the tomato purée, then the rosemary and bay leaf. Season well with salt and pepper. Return the lamb shanks to the GN container, pour over the stock and cover with a lid. Set the combi oven to combination mode 130°C, 70% humidity, fan speed 60%, for 4 hours. Prepare the mash. Steam the potatoes and jerusalem artichoke in a stainless stell GN container using the steam mode 99°C for 20 minutes . Warm the milk and butter in a small pan until just boiling then remove from the heat. Transfer the cooked potatoes and jerusalem artichokes into a bowl and add the milk and butter mixture and mash until smooth. Season it. When the lamb shanks are cooked remove them from the sauce, pass the sauce through a sieve and place in a pot and reduce it to a thick cosistence.