Prepare and Brown the Beef: In a large bowl, toss the beef cubes with the 2 tbsp of plain flour, salt, and pepper until evenly coated. Heat the olive oil in a large, heavy-based casserole dish or Dutch oven over a medium-high heat. Working in two batches to avoid overcrowding the pan, brown the beef on all sides until a deep crust forms, about 5-7 minutes per batch. Remove the browned beef with a slotted spoon and set aside.

Sauté the Vegetables: Lower the heat to medium and add the chopped onions, carrots, and celery to the same pot. Cook for 8-10 minutes, stirring occasionally, until they have softened and the onions are translucent. Add the minced garlic and cook for another minute until fragrant.

Create the Gravy Base: Stir in the tomato purée and cook for 2 minutes, allowing it to caramelise slightly. Pour in the red wine to deglaze the pan, scraping up any browned bits from the bottom with a wooden spoon – this is pure flavour! Let the wine bubble and reduce by about half. For a deeper understanding of building flavour at this stage, you can learn more about creating a foundational roux and gravy base.

Simmer the Filling: Return the browned beef to the pot. Pour in the beef stock and add the thyme sprigs, bay leaf, and Worcestershire sauce. Stir everything together and bring to a gentle simmer. Once simmering, reduce the heat to low, cover with a lid, and let it cook very gently for at least 2 hours, or until the beef is meltingly tender. I find that checking after 90 minutes is a good idea, but it almost always needs the full 2 hours.

Finish and Cool the Filling: Once the beef is tender, remove the pot from the heat. Fish out the thyme sprigs and bay leaf. Stir in the frozen peas and season the filling with more salt and pepper to taste. To prevent a soggy bottom on your pie, it's essential to let the filling cool down. You can transfer it to your pie dish and leave it to cool to room temperature, or even chill it in the fridge for an hour.

Assemble the Pie: Preheat your oven to 200°C (180°C fan). Unroll the puff pastry. Place your pie dish upside down on the pastry and cut around it, leaving a 2cm border. Use the pastry trimmings to cut a long strip to line the rim of your pie dish. Brush the rim of the dish with a little beaten egg, then press the pastry strip onto it.

Add the Lid and Bake: Brush the pastry rim with more egg. Carefully lay your pastry lid over the filling, pressing the edges down firmly to seal. You can crimp the edges with a fork if you like. Brush the entire lid with the remaining beaten egg and make 2-3 small slits in the centre to allow steam to escape.

Bake to Perfection: Place the pie on a baking tray (to catch any potential drips) and bake for 25-30 minutes, or until the pastry is puffed up, deeply golden brown, and the filling is bubbling hot. Let it rest for 10 minutes before serving.