Preheat the oven to 180°C.
Fry the lamb and kidneys in olive oil for 2 minutes until golden-brown and set aside.
Soften the onions with salt in the same pan and stir in the flour.
Simmer the stock, thyme, bay leaves, and Worcestershire sauce for 10 minutes until thickened.
Layer potatoes, seasoned with salt and pepper, lamb mixture, black pudding, and stock in a buttered casserole dish.
Finish with a layer of potatoes dotted with butter.
Bake covered for 20 minutes, then uncover and bake for 20 more minutes until golden-brown.
Spoon into serving bowls to serve.