Brown the lamb

• Heat the olive oil in a large frying pan over high heat.
• Add the lamb mince and brown it well, breaking it up with a spoon.
• Season with salt and pepper.

Soften the vegetables

• Add the onion, carrots, celery and garlic to the pan.
• Cook, stirring, until softened and fragrant.

Build the filling

• Stir in the tomato purée and cook for a minute.
• Sprinkle over the flour and stir to coat.
• Pour in the lamb stock and Worcestershire sauce, then simmer until thickened.

Add the peas

• Stir the frozen peas into the meat mixture.
• Taste and adjust the seasoning, then set aside.

Boil the potatoes

• Put the potatoes in a saucepan of salted cold water.
• Bring to the boil and cook until tender.

Mash the potatoes

• Drain the potatoes and let them steam dry.
• Mash with the butter and milk until smooth.
• Stir in the grated parmesan and season to taste.

Assemble the pie

• Heat the oven to 200 °C.
• Spoon the meat filling into a baking dish.
• Top with the mashed potato and spread it evenly, roughing up the surface with a fork.

Bake

• Bake until the top is golden and the filling bubbles at the edges.
• Let it rest for a few minutes before serving.