Preheat the oven to 425°F (220°C).
In a large skillet, heat the olive oil over medium heat. Add the sliced onion and cook until softened, about 5 minutes. Add the minced garlic and cook for an additional minute.
Add the beef stew meat to the skillet. Season with salt, black pepper, and thyme. Brown the meat on all sides, about 5-7 minutes.
Stir in the Worcestershire sauce and beef broth. Bring to a simmer, then cover and reduce heat to low. Let it cook for 1 hour, stirring occasionally.
In a small bowl, mix the cornstarch and water to create a slurry. Add this to the skillet and stir until the mixture thickens, about 2-3 minutes. Remove from heat and let cool slightly.
Roll out one pie crust and place it in a 9-inch pie pan. Fill with the beef and onion mixture.
Roll out the second pie crust and place it over the filling. Seal the edges by crimping with a fork. Cut a few slits in the top crust to allow steam to escape.
Brush the top crust with the beaten egg for a golden finish.
Bake in the preheated oven for 25-30 minutes, or until the crust is golden brown. Let cool for 10 minutes before slicing.