Preheat the oven to 180°C.
Heat olive oil in a large frying pan and brown the lamb and kidneys for 3 minutes.
Fry the onions and carrots for 4 minutes until softened and remove from heat.
Butter a casserole dish and line it with a seasoned layer of sliced potatoes.
Layer the meat, carrots, onions, kidneys, and herbs into the dish and season.
Add another layer of overlapping potato slices on top.
Mix Worcestershire sauce with beef stock and pour into the dish until it reaches the top potato layer.
Brush the top layer of potatoes with 50g of melted butter.
Bake covered for 2 hours, then uncovered for 30 minutes until golden.
Serve generous portions with pickled beetroot on the side.