Slice the potatoes finely, using a mandolin if possible
Heat a casserole dish with a little oil over a medium heat stove
Cook the lamb with the sliced onions until brown, then add the celery and carrots
Lay the Rudd’s Roulade on top of the celery and carrots, then layer one layer of potatoes on top of the Roulade. They should overlap slightly and form a pretty circular pattern
Sprinkle parmesan cheese over this layer of potatoes and repeat the sliced potato layer again, but this time leave a hole in the centre
Top the potatoes with thyme leaves and ground black pepper then pour the hot stock into the hole and fill up to just below the potatoes.
Cover the casserole with a lid and bake for 35 minutes
Remove the lid, and return the uncovered casserole to brown in the oven for 5 more minutes before serving