Heat olive oil in a large Dutch oven over medium-high heat. Season beef cubes with salt and pepper, then brown them in batches until deeply caramelized on all sides. Remove beef and set aside.

In the same pot, add onions, carrots, and celery. Cook until softened, about 5-7 minutes. Add garlic and cook for another minute until fragrant.

Sprinkle flour over the vegetables and stir to coat. Gradually add beef broth while stirring constantly to prevent lumps. Add tomato paste, Worcestershire sauce, thyme, and bay leaf. Return the beef to the pot.

Bring the mixture to a simmer, then reduce heat to low. Cover and cook for 1.5-2 hours until beef is fork-tender. Stir in frozen peas during the last 5 minutes of cooking. Remove bay leaf and let the filling cool slightly.

Preheat oven to 400°F (200°C). Transfer the beef stew filling to a 9-inch pie dish. Roll out one sheet of puff pastry to fit over the dish. Brush the rim of the dish with egg wash, then place the pastry over the filling. Press edges to seal and trim excess pastry.

Brush the top crust with egg wash and cut a few slits for steam to escape. Bake for 25-30 minutes until the crust is golden brown and flaky. Let rest for 10 minutes before serving.