Begin by removing lamb from the fridge and allowing the lamb to come to room temperature.
Pre heat the oven to 200 degrees Celsius.
Combine all ingredients bar the butter in either a pestle and mortar or a food processor and ground or throughly combine, add in the butter again mix until thoroughly combined.
Lay out the breast of lamb then smother once side with the rosemary butter, roll the lamb and knot the string around it as tightly as possibly then transfer to the oven, cook on 200 degrees Celsius for 20 minutes so the outside crispens up then reduce the heat to 160 degrees Celsius, cover with foil and allow to cook for 4 hours. At 4 hours have a look and see how it’s doing, depending on how generous/thick and meaty the lamb breast is you might want to let it cook for another hour. The lamb should very easily be pulled apart.
Serve with Grandad’s Mint Sauce
Finely chop the mint leaves then sprinkle over half of the sugar and continue to chop , combining the sugar and mint leaves, transfer to a jug and add the vinegar, stir and taste, add more sugar if you prefer it sweeter or more vinegar for it sharper.
Serve with a large portion of mash, roast potatoes, braised red cabbage or greens.