Preheat your oven to 325°F (160°C). Season the cubed beef generously with salt and pepper, then toss with 2 tablespoons of flour to coat evenly.

Heat the vegetable oil in a large oven-proof pot or Dutch oven over medium-high heat. Add the beef in batches and sear until browned on all sides, then remove the meat and set it aside.

In the same pot, reduce heat to medium and add the chopped onion. Sauté for about 5 minutes until softened and translucent, then stir in the minced garlic and cook for another minute until fragrant.

Pour in the stout beer and beef broth, using a wooden spoon to scrape up any browned bits from the bottom of the pot. Return the browned beef to the pot along with the thyme and bay leaf.

Bring the mixture to a simmer, cover with a lid, and transfer to the oven. Cook for about 1 hour and 30 minutes, or until the beef is very tender.

Remove the pot from the oven and increase the oven temperature to 400°F (200°C). If the sauce is too thin, simmer on the stove for a few minutes to thicken, then stir in the shucked oysters gently.

Transfer the beef and oyster mixture into a deep pie dish. Roll out the thawed puff pastry on a lightly floured surface so it is slightly larger than the dish.

Place the pastry over the filling, pressing the edges down to seal against the rim of the dish. Cut a few small slits in the center to allow steam to escape.

Brush the top of the pastry with the beaten egg wash for a glossy finish. Bake for 20-25 minutes, or until the pastry is puffed and golden brown.

Let the pie rest for 10 minutes before serving to allow the filling to settle. Serve hot with mashed potatoes or steamed green vegetables.