Heat the oil in a thick-bottomed frying pan, season and fry the meat on a high heat, stirring occasionally. In another pan gently cook the onions and thyme in a little more oil for 3-4 minutes until soft, then add the meat and stock, season, bring to the boil and simmer with a lid on for 1 1/2 hours. Add the potatoes and cook for a further 15 minutes.
Pre-heat the oven to 180C/gas mark 5.
Making the pastry:
mix the flour and salt with the suet and grated butter. Mix in about 150ml of water to form a smooth dough and knead for a minute. Roll the pastry on a floured table to about 1cm thick and cut out to about 2cm larger all the way round than the pie dish you are using.
Add the meat to the dish or dishes you are using, then brush the edges of the pastry with a little of the beaten egg and lay the pastry on top of your pie, pressing the egg-washed sides against the rim of the dish. Cut a small slit in the top of each pie to allow steam to escape, and brush with beaten egg. Leave to rest in a cool place for 30 minutes.
Cook for 40-50 minutes until golden.