Heat a lidded casserole dish and add the oil and butter. Once melted, add the lamb in batches and fry until browned all over. Remove from the pan and set aside.
Add the bacon lardons to the pan and cook for 1-2 minutes or until crisp. Add the spring onions, garlic and sage and cook for a further 2-3 minutes. Add the butternut squash and sweet potato mix and stir. Add the sun-dried tomatoes, flour, mushrooms, jam and bay leaf and cook for a further 1-2 minutes.
Return the sealed lamb to the pan along with the Worcestershire sauce and port. Cook until the port has reduced by half. Add the stock, mustard powder and season with salt and pepper stir. Cover with the lid and transfer to the oven for 20 minutes.
For the dumplings, place the flour, suet and thyme leaves into a large glass bowl and mix to combine. Add the egg and 50ml/2fl oz water, mix and bring to a dough. Roll the mixture into 12 evenly-sized dumplings.
Remove the stew from the oven and stir in most of the parsley.
Place the dumplings on top of the stew and place back in the oven with the lid on for 10 minutes. Remove the lid and cook for a further 15-20 minutes, or until the dumplings are golden-brown.
To serve, spoon some of the stew and dumplings into shallow serving bowls and garnish with the remaining parsley.