Peel and dice the onion, carrot, celery and garlic.
Glug the oil into a medium hot pan and add the onion, carrot and garlic.
Fry gently until the onions soften.
Turn the heat right up before adding the lamb mince.
Brown the lamb mince well, then add the tomato purée to coat everything.
Pour in the passata, followed by the stock and the Worcestershire sauce.
Let the lamb mixture simmer gently for about an hour, until the liquid reduces to a thick sauce.
Peel the potatoes and place them into a large saucepan.
Cover the potatoes with cold water, season with salt and heat it to a boil.
Boil for 20-25 minutes, until the potatoes are soft, but not falling apart.
Drain the potatoes, then return them to a pan and mash well.
Place the potatoes back on the heat and pour in the milk, a little at a time, and add the butter.
Continue mashing until the potatoes are smooth.
Preheat the oven to 200ºC.
Pour the lamb mixture into a deep baking dish.
Spread the mash over the top to seal the mince in.
Crumble the blue cheese over the mash.
Place the dish into the oven for 15-20 minutes, until the top is golden and bubbling. Then serve the whole dish at the table with fresh steaming veg and let everyone dig in!