Stab the potatoes a few times all over, then coat in olive oil & salt. Bake at 356F/180c for 80mins, or until deep golden, crispy & knife tender.
Once cool enough to handle, slice off the top (¾ of the way up) & scoop out most of the centre into a large bowl, leaving a thin wall to keep the potato sturdy. Mash the potato with butter, milk, nutmeg, half of the cheese and plenty of salt & pepper to taste (I typically use ½ tsp salt & ¼ tsp pepper).
Meanwhile, in a large pan over medium heat add a drizzle of oil alongside the carrot, onion, garlic & mushrooms. Fry until soft and starting to pick up colour, then add in the beef & fry until brown all the way through, breaking up with your wooden spoon as you go.
Stir in tomato puree & fry for a couple of mins, then pour in the wine. Simmer for a few mins, then pour in beef stock. Stir in rosemary, thyme, gravy granules, Worcestershire sauce and salt & pepper (to taste). Reduce heat to low and gently simmer for around 20-25mins to thicken the sauce.
Spoon the beef into the potatoes, then top with a few heaped tbsp of potato. You should be left with 1 cup of mash, save it in the fridge for a rainy day. Top potatoes with cheese, then place back in the oven at 220C/430F for around 12-15mins, or until golden & bubbly!
