Step 1

Heat oven to 140C/120C fan/gas Put the lamb on a chopping board. In a small bowl, mix the garlic, 1 tbsp flaky salt, rosemary and mustard into a paste. Rub on the inside of each lamb breast. Next, stack the breasts on top of each other and roll up the longest side into a sausage shape. Use the butchers string to tie knots along the length of the lamb.

Step 2

In a large, round casserole dish, heat the duck fat. When it reaches 100C on a cooking thermometer, add the lamb (you may need to curl it into the dish). Put the lid on, then cook in the oven for 4 hrs until tender. Remove the dish and leave to cool. Once the fat is cool enough, remove the lamb using two slotted spoons. Reserve the cooled fat as you will need 1 tbsp tomorrow, and save the rest to make roasties. Lay the lamb roll on some cling film, then roll as tight as you can. Chill on a baking tray in the fridge overnight.

Step 3

The next day, heat oven to 180C/ 160C fan/gas Remove the cling film and string, and slice into 6-8 equal portions. On a plate, mix the flour and polenta, and season well. Dip each portion into the mixture. Meanwhile, heat 1 tbsp of duck fat in an ovenproof frying pan.

Step 4

When the pan is hot, add the lamb. Seal each side for 2-3 mins until you get a golden, crispy crust. Sear the sides, then transfer the pan to the oven for 8 mins or until it’s hot in the middle. Remove from the oven and put the lamb on a plate loosely covered with foil.

Step 5

Carefully put the pan back on the hob – you should have a good layer of lamb fat. Add your butter then, once foaming, add the shallots, broad beans and chilli. Stir-fry for 1 min, then add the vinegar and marjoram leaves. Season to taste, then remove from the heat. Serve immediately with the crispy lamb breast and reduced lamb stock.