Lancashire hot pot

Name: Lancashire hot pot
Ingredients: 2 tbsp olive oil; 1kg/2lb 2oz neck of lamb, chopped into bite-sized pieces; 4 lambs' kidneys, cleaned, trimmed, cut into quarters; 2 onions, peeled, sliced; ½ tsp salt; 1 tbsp plain flour; 250ml/9fl oz lamb stock; 1 sprig fresh thyme; 2 fresh bay leaves; 1 tbsp worcestershire sauce; 50g/2oz butter, cut into cubes, plus extra for greasing; 2 x 250g/7oz black pudding rings, outer casing removed, thickly sliced; 1kg/2lb 2oz potatoes, peeled and sliced; Salt and freshly ground black pepper