2 handfuls sprout leaves or baby sprouts, broken into leaves
75g/2½oz unsalted butter
To make the lamb, preheat the oven to 160C/140C Fan/Gas 3.
Pierce the lamb all over with a sharp knife and stuff the anchovies, garlic and rosemary into the holes. Place in a large roasting tray and cook for 3–4 hours.
To make the Jansson’s temptation, turn the oven up to 180C/160C Fan/Gas 4. Spread a third of the potatoes in an oven-proof baking dish and top with half of the anchovies and half of the onion then repeat again and finish with a layer of potatoes. Season with salt and pepper, dot the butter over the top and pour the cream over. Sprinkle with the breadcrumbs and bake for 1½ hours, until golden and cooked through.
To make the sprout tops, heat the butter in a large frying pan and sauté the sprouts over a high heat until cooked.
To serve, slice the lamb and serve on plates alongside the Jansson’s temptation and sprouts. Drizzle with gravy.