Dust the ribs with flour and season liberally with salt.
Fry them in batches until browned all over.
Fry the pancetta until crispy then add the mushrooms and sauté until soft and golden.
In a large roasting tray place the mushrooms, pancetta and ribs. Add thyme and pour over the red wine and stock then bring up to a gentle simmer - take away and braise for at least five hours, or until the ribs are tender to a fork. Shred, remove the meat and reduce the sauce to make a lovely thick gravy.
Meanwhile, mix the potatoes, eggs, cream and parmesan. Season to taste and place in a piping bag with a large star nozzle.
Blind bake the puff pastry for 20 minutes and pour over the shredded beef and gravy. Top with swirls of mash stuffed with cubes of gruyere.