Season the beef cubes generously with salt and pepper. Heat olive oil in a large Dutch oven over medium-high heat. Brown the beef in batches, ensuring each piece gets a nice sear on all sides.

Reduce heat to medium and add the onion, carrots, and celery to the pot. Cook for 5-7 minutes until vegetables begin to soften. Add the minced garlic and cook for another minute until fragrant.

Sprinkle the flour over the vegetables and beef, stirring constantly for 2 minutes to cook out the raw flour taste. Gradually pour in the beef broth while stirring continuously to prevent lumps. Add Worcestershire sauce, thyme, and bay leaf.

Bring the mixture to a simmer, then reduce heat to low, cover, and cook for 1.5-2 hours until the beef is fork-tender. Stir occasionally to prevent sticking. Remove from heat, stir in frozen peas, and discard the bay leaf.

Preheat oven to 400°F (200°C). Transfer the beef filling to a 9-inch pie dish. Roll out one sheet of pastry to fit the top of the dish. Place over the filling, trim excess, and crimp edges. Cut slits in the top for steam to escape. Brush with beaten egg for a golden finish.

Bake for 30-35 minutes until the crust is golden brown and the filling is bubbling. Let rest for 10 minutes before serving to allow the filling to set.