Bring a large pot of salted water to a boil. Add the potatoes and cook until tender, about 12-15 minutes.Drain the potatoes, then mash with the milk, butter, and a pinch of salt until smooth and creamy. Set aside.

In a large pan, heat a little oil and a tbsp of butter over a medium heat. Add the chopped onion, carrot, and leek. Cook for 5-7 minutes, stirring occasionally, until softened, then add the tomato paste and cook for a further 2. Add the beef mince to the pan and cook until browned, breaking it up with a spoon as it cooks.

Pour in the red wine, and allow it to simmer for 2-3 minutes until reduced then add the semi-dried rosemary, thyme, and beef stock. Stir to combine, then simmer the mixture for 25-30 minutes until the liquid has reduced and the flavours have melded. Season with salt and pepper to taste.

Preheat the oven to 200°C. Transfer the beef mixture into an ovenproof dish, spreading it out evenly. Spoon the mashed potatoes over the beef filling, smoothing them out with the back of a spoon or fork. For a crispy top, you can create some texture by making ridges or peaks with the fork.

Place the cottage pie in the oven and bake for 20-25 minutes, or until the top is golden brown and the filling is bubbling around the edges. Allow the pie to cool slightly before serving and enjoy.