STEP 1:

To make the stuffing, heat the oil in a frying pan over a medium heat. Add the onion and fry, stirring, for about 10 minutes, until golden. Add the garlic and fry for a couple of minutes more then take off the heat. Add the thyme, prunes and pine nuts and season well with salt and pepper. Leave to cool completely.

STEP 2:

Preheat the oven to 200°C/gas 6.

STEP 3:

Open out the lamb on a board, skin side down. Use a sharp knife to make some deep slashes into the thicker parts of the meat, then lay a sheet of parchment over the meat and use a rolling pin or meat mallet to beat it (just a bit – no need to go mad!) into a reasonably even, roughly rectangular shape. Discard the parchment.

STEP 4:

Have ready 3-4 long pieces of cotton string. Season the surface of the meat with salt and pepper, then spread the cooled stuffing over it, leaving a gap at one shorter end and along both longer ends – the stuffing will fill up these gaps as you roll the meat. Press the stuffing into the slashes and crevices in the meat. Now roll up the meat as snugly as you can, working towards the shorter end with the gap. It doesn’t need to be super tidy! Use the pieces of string to secure the meat firmly in its rolled-up shape. Scoop up any stuffing that escapes and push back into the joint. Weigh the joint now.

STEP 5:

Transfer the meat to a roasting dish. Brush it all over with oil and season well with salt and pepper. Put the roughly chopped onion and celery around the meat, and the bay leaf if using, and pour 200ml water into the tin. Calculate the cooking time at 20 minutes per 500g stuffed weight (you should get a total between 1¼ and 1½ hours). Put the meat in for this time.

STEP 6:

If you have a probe thermometer: the meat should reach around 60C in its thickest part for medium, and around 70C for medium-well done.

STEP 7:

Transfer the meat to a warmed dish and cover with foil while you make the gravy.

STEP 8:

Tip all the juices from the roasting tin, along with the veg and any stray bits of stuffing, into a saucepan over a medium heat. Sprinkle over the flour and whisk it in. Let the juices come to a simmer and thicken. Gradually whisk in the hot stock and any more juices that have seeped from the resting lamb joint, and bring to a simmer again. Cook for a couple of minutes then taste the gravy. If it seems good, add salt and pepper to taste, pass it through a sieve into a warmed jug, squishing the veg in the sieve to extract maximum flavour, and it’s ready to serve. If you feel the flavour could be a little more intense, simmer the gravy down for a bit longer until it tastes good to you before seasoning and sieving.

STEP 9:

Serve the lamb in thick slices with the gravy, new potatoes and spring veg.