Directions

1. Heat the oil in a large flameproof casserole dish and brown the lamb shanks well all over (you may need to do this in batches). Transfer the lamb to a plate. Reduce the heat, tip the onions into the dish and gently soften, adding a splash more oil if you need to. Stir in the rosemary for the final 1 min, then add the thyme and wine. Bring to a fierce simmer, scraping all the lamb bits off the bottom of the dish as you go - these will add lots of flavour. When the wine has boiled for 1 min, add the stock, return the shanks and any juices, and gently bring to a simmer. Cover with a tight-fitting lid, reduce the heat a little and cook until the meat is very tender and falling from the bone - this can take 2-3 hrs. Leave until cool enough to handle.Can be done 24 hrs ahead, covered and chilled, or frozen for up to a month.
2. Lift the shanks out of the stock (at this stage you can spoon off any fat that has separated to the surface). Gently pull the meat off the bones in nice big chunks, discarding any fatty bits, and put in a pie dish - about 30 x 20cm and 5cm deep will be big enough.
3. Put the stock back on the heat and boil fiercely until reduced by just under half. Meanwhile, in a big frying pan, melt the butter, then stir in the flour to a paste and cook for 1-2 mins. Gradually whisk in ladlefuls of the reduced stock until you have a smooth sauce. Bubble for a few mins to thicken up nicely (the sauce will thin a little when cooked in the pie). Taste for seasoning, then tip over the lamb.
4. To make the pastry, put the flour, butter, suet and 1 tsp salt in a food processor, and whizz together until no lumps of fat remain. With the motor running, gradually pour in 150ml water to bring the pastry together - you may need 1 tsp more water. Tip onto a lightly floured work surface and gently bring together to a smooth dough, then roll out until just over 0.5cm thick.
5. Add the frozen peas, spring onions, parsley and mint to the lamb, and gently mix to combine. Brush the rim of the dish with a little egg, then cut thin strips of pastry and stick them on the rim, like a picture frame. Lift the rest of the pastry onto the pie and press down to the edges to stick. Trim the excess and crimp the edges to seal well. Make a small cross in the centre with a knife to help steam escape, and roll the trimmings into leaves, if you like. Stick these all over the pie, again using egg, to decorate.Can now be chilled for another 24 hrs or frozen for up to a month.
6. Heat oven to 200C/180C fan/gas 6. Brush the whole pie with more egg, then bake for 40-45 mins until really golden and crisp.