Step 1

Put the lamb bones, herbs and stock vegetables into a pressure cooker

Step 2

Cover with at least a litre of cold water

Step 3

Set the pressure to high and the timer to one hour

Step 4

Once the stock is cooked, release the pressure naturally

Step 5

If you prefer, make this on a hob by filling a stock pot, bringing to the boil and simmering for 2 hours.

Step 6

Strain the liquid and allow to cool before refrigerating

Step 7

Preheat the oven to 190C (fan) or 200C (conventional oven)

Step 8

Season the flour with plenty of salt and pepper

Step 9

Peel and slice the onions into rounds about 1/2cm thick

Step 10

Peel and slice the potatoes into rounds about 1/2cm thick

Step 11

Trim the carrots and celery and dice them into 1cm pieces

Step 12

Put half the butter into a large, deep saute pan and melt over a moderate heat

Step 13

Add the onion slices and rosemary, season with salt and pepper and cook gently for 6-8 minutes. Add the carrots and celery for the last 2 minutes of cooking

Step 14

Meanwhile, sprinkle the flour over the lamb and mix well.

Step 15

Once the onions are soft, set to one side and add the remaining butter to the pan so that it melts, then take it off the heat

Step 16

Add the potatoes and season well with salt and pepper. Toss the potatoes around gently so all the pieces get coated with butter

Step 17

Spread the lamb out across the base of a heavy roasting pan or shallow casserole

Step 18

Top the lamb with the onion and vegetable mixture.

Step 19

Now layer in the potatoes, overlapping the slices as neatly as possible.

Step 20

Heat up the lamb stock (I did this in the microwave) till it's nearly at boiling point

Step 21

Pour it gently into the casserole

Step 22

Cover the casserole with a lid or with foil and put it into the oven

Step 23

Cook for 45 minutes covered, then remove the lid or foil and continue to cook for a further 45 minutes. Check regularly to make sure the potatoes are not overcooking

Step 24

Serve with buttered green vegetables