1. Preheat the oven to 160°C/325°F/gas mark 3. Toss the lamb together with the flour and a good pinch of salt and pepper until evenly coated. Heat a little oil in a 2 litre Pyroflam casserole then fry the lamb in batches until golden brown. Transfer to a plate and set aside.
2. Add a little more oil to the pan then fry the onions for 3-4 minutes until starting to colour. Return the lamb to the casserole then add the thyme, carrots, stock and Worcestershire sauce and stir to combine. Season to taste.
3. Arrange the potato slices in an even layer on top of the meat then cover with a lid and cook in the oven for 1 ½ hours.
4. Turn the oven up to 200°C/400°F/gas mark 6. Remove the lid from the casserole and brush the potatoes generously with the melted butter. Bake for a further 25-30 minutes until the potatoes are golden brown and crisp. Leave to cool slightly then serve with simple vegetables such as red cabbage and winter greens.