Preheat your oven to 180°C/Fan 160°C/Gas 6. Peel the onions and slice them thinly. Dice the carrot into small pieces. Peel and thinly slice the garlic cloves. Trim the ends off the celery stick and thinly slice it.

Pour 1 tbsp olive oil into a large ovenproof pan and warm to a medium-high heat (if your pan isn't ovenproof, see our tip at the end). Tip the flour onto a plate and add the diced lamb and a good pinch of salt and pepper. Toss the lamb in the flour till it's completely coated. Add the lamb to the pan (save the plate of flour for later). Fry the lamb for 3-4 mins, turning once or twice, till well browned. Lift the lamb out of the pan and into a bowl.

Return the pan used to cook the lamb to a medium heat (no need to clean it). Slide in the chopped onions, carrot, garlic and celery. Add the rosemary leaves and fry for 5 mins, till the veg have slightly softened. Tip in the reserved flour and stir for 2 mins.

While the veg fry, thinly slice the cavolo nero leaves. Crumble the stock cube into the pan and add 1 tbsp Worcester sauce. Pour in 300ml boiling water. Tip the browned lamb back into the pan, along with the sliced cavolo nero. Stir well and bring to the boil.

Scrub the potatoes and slice them, as thinly as possible, into rounds. When the lamb stew is simmering, spread the sliced potatoes, overlapping slightly, evenly over the surface. Brush the potatoes with 1 tsp oil and a pinch of salt and pepper. Slide the pan into the oven and cook for 30 mins, till the potatoes are tender.

While the pie is cooking, trim and halve the Brussels sprouts. When the pie is nearly ready, pour 1 tbsp olive oil into a large frying pan and warm to a medium heat. Add the Brussels sprouts and a pinch of salt and pepper. Fry for 4-5 mins, stirring occasionally, till the sprouts are tender. Squeeze in the juice from half the lemon.

Divide the potato and lamb pie between a couple of warm plates and serve with the lemony panfried sprouts on the side.