Cut steak into 3cm cubes and season. Heat 2tbsp of oil in frying pan and over a high heat fry meat till well browned all over. Do this in 2 batches to avoid 'steaming' meat add extra tbsp of oil if pan is dry. Place beef in casserole dish and toss it in flour.
Heat oven to Gas 2 150C/130C fan. add 1 tbsp oil to pan and cook the onions and garlic over a medium heat for 5-10 mins until golden and soft then mix with beef in casserole dish. Deglaze pan with red wine (or water) and Worcestershire sauce and bring to boil whilst stirring and lifting any residue from the pan.
Pour sauce over the beef add stock and bay leaf. Bring to boil on top of stove then cover with lid and cook in oven for 1.5 hours.
Meanwhile, melt butter in frying pan and cook mushrooms for 5 mins until lightly browned, then add to beef and return casserole for another 30 mins (2-hr total). Remove from oven and cool.
To make the pastry rub the butter into the flour with a generous pinch of salt and mix with fingertips until mixture resembles fine breadcrumbs. Stir in egg and water mixture, bring together to form a dough and knead very lightly. Divide the dough into 2/3'ds for base and 1/3'ds for the top. Roll into balls, flatten slightly, wrap each ball in cling film and chill for 20 mins. If preparing dish early in day (or day before) you can prepare to this point and store filling and dough in fridge until next day or when ready to assemble. Remember to bring dough to room temperature before rolling.
Heat oven to gas 6 200C/180C fan. Roll out larger ball of pastry and use to line a greased 23cm (9") pie dish. HANDY TIP!! To avoid a soggy base, sprinkle the pastry base with a spoonful of semolina then spoon in beef, onions and mushrooms using a slotted spoon, adding just enough of the liquid to be "saucy." Save remaining sauce and gently reheat and serve with finished pie. Brush the pastry rim with a little beaten egg. Roll out the smaller ball of dough for the pie top and gently lay it over the filling. Use a sharp knife to trim any overhanging pastry (you can use surplus to decorate top of pie). Crimp edges with fingers or fork, brush with beaten egg to glaze. Bake in oven for 30 mins until pie is golden brown and filling is piping hot. Serve with heated gravy.