Heat olive oil in a large pot over medium-high heat.
Brown beef cubes in batches; remove and set aside.
Sauté onion and garlic until softened.
Add mushrooms and cook until browned.
Sprinkle flour and cook briefly.
Stir in beef stock, Worcestershire sauce, thyme, and bay leaf.
Return beef to pot; simmer covered until tender (60–75 minutes).
Let filling cool slightly.
Prepare pastry by cutting butter into flour and salt, then add water.
Roll out pastry and line pie dish.
Fill with beef mixture, cover with top crust, seal edges.
Brush with egg wash.
Bake at 400°F (200°C) for 30–35 minutes until golden.