Preheat Oven: Preheat your oven to 350°F (175°C).

Prepare the Beef: Toss the cubed beef with the flour, ensuring it’s evenly coated.

Brown the Beef: Heat the vegetable oil in a large ovenproof pot or skillet over medium-high heat. Brown the beef in batches, ensuring all sides are seared. Remove the beef and set aside.

Sauté Vegetables: In the same pot, add the onions, carrots, and garlic. Cook for 5 minutes, stirring occasionally, until softened.

Deglaze the Pot: Pour in the red wine or ale (if using) and scrape the bottom of the pot to release any browned bits. Let it simmer for 2 minutes.

Simmer the Filling: Return the beef to the pot. Add the beef stock, Worcestershire sauce, thyme, bay leaf, salt, and pepper. Stir well, bring to a simmer, cover, and transfer to the oven. Cook for 2 hours, or until the beef is tender and the sauce has thickened.

Prepare the Pastry: Remove the pot from the oven and transfer the filling to a deep pie dish. Roll out the puff pastry and place it over the dish, trimming any excess. Press the edges to seal and crimp with a fork.

Apply Egg Wash: Brush the beaten egg over the pastry to give it a golden finish.

Bake the Pie: Increase the oven temperature to 400°F (200°C). Place the pie in the oven and bake for 20-25 minutes, or until the pastry is puffed and golden brown.

Serve: Let the steak pie rest for 5 minutes before serving with mashed potatoes and steamed vegetables, if desired.