Classic Shepherd's Pie

Place the peeled and quartered potatoes in a large pot, cover with cold salted water, and bring to a boil. Cook for 15-20 minutes, or until fork-tender. Drain well, then return to the hot pot over low heat for a minute or two to dry out. Mash thoroughly, then beat in the butter, milk, salt, and pepper until smooth and creamy. Set aside.

Preheat your oven to 190°C (375°F). Heat the olive oil in a large, oven-safe frying pan or a heavy-bottomed pot over medium-high heat. Add the lamb mince and cook, breaking it up with a spoon, until evenly browned. Drain off any excess fat.

Reduce the heat to medium. Add the chopped onion, carrots, and celery to the pan with the mince. Cook for 8-10 minutes, stirring occasionally, until the vegetables have softened. Add the minced garlic and cook for another minute until fragrant.

Stir in the plain flour and tomato paste, cooking for 1 minute to coat the mince and vegetables. Pour in the beef stock and Worcestershire sauce, stirring constantly to prevent lumps. Add the rosemary or thyme sprig if using. Bring the mixture to a simmer, then reduce the heat to low and let it gently bubble for 10-15 minutes, allowing the sauce to thicken and flavours to weld.

Remove the rosemary or thyme sprig. Stir in the frozen peas and cook for another 2-3 minutes until heated through. Taste and adjust seasoning with salt and pepper as needed.

Pour the mince mixture into an ovenproof dish (if not already using one). Spoon the mashed potato evenly over the mince filling, spreading it to the edges. You can use a fork to create ridges on top for a crispier finish.

Bake in the preheated oven for 20-30 minutes, or until the potato topping is golden brown and the filling is bubbling around the edges.

Let the pie rest for 5-10 minutes before serving.