Step 1 Remove the leg of lamb from the fridge an hour before cooking to allow it to come to room temperature.

Step 2 Place the sliced onions in the base of an AGA Roasting Tin and season. Lay the lamb on top.

Step 3 Cut a diamond pattern on the top of the leg of lamb, making some deep slits to take the purée.

Step 4 To make the purée; place the lemon zest, mint leaves, oil, garlic and seasoning into a small food processor and whizz together.

Step 5 Stuff into the incisions made in the lamb. Any extra can be smeared over the sides of the meat and onto the bed of onions. Place the fennel wedges around the lamb.

Step 6 Slide the roasting tin onto the lowest set of runners in the AGA roasting oven and roast for about 1 hour to 1 hour 15 minutes or until done to your liking.

Step 7 Check with a meat thermometer 55º-60ºC will be medium and 70ºC for well done – place the thermometer into the thickest part of the meat, but not touching the bone.

Step 8 Remove the lamb from the roasting tin and place on a warm serving dish. Cover with some foil and allow it to rest in a warm place (such as the AGA warming oven) for 15-20 minutes.

Step 9 Meanwhile, check the fennel is nicely golden and cooked – if it needs more cooking, or more colour, pop the tin back into the roasting oven.

Step 10 To make the sauce, firstly remove the fennel and keep warm. Add the flour to the cooked onions, stir well and heat until the flour is browned.

Step 11 Add the Worcestershire Sauce and vegetable stock (water from boiling any vegetables is fine), the amount of vegetable stock will vary according to how thick you like your sauce.

Step 12 Bring to a boil and simmer for a couple of minutes until thickened, check for seasoning and serve in a sauce boat or warm jug. The sauce could be liquidised if preferred.

Step 13 Serve the lamb with the fennel wedges, sauce and seasonal vegetables.