- STEP 1
1. Preheat the oven to 180°C, fan 160°C, gas 4. Put the potatoes in a large pan, cover with cold water and boil for 15 minutes, until tender. Drain. Meanwhile, in another pan, boil the cabbage and leeks for 5 minutes. Drain, add to the potatoes and mash together with the butter and milk. Season with freshly ground black pepper. Set aside.
- STEP 2
2. Heat the oil in a large pan over a medium heat. Add the onion and carrot and cook for 5 minutes, until softened. Add the mushrooms and cook for a further 5 minutes.
- STEP 3
3. Put the leftover roast beef in a small bowl, add the flour and toss to coat. Add to the pan along with the tomato purée, chopped tomatoes, beef stock, Worcestershire sauce and dried herbs. Simmer, uncovered, for 15 minutes.
- STEP 4
4. Transfer the beef mixture to a 1.5-litre baking dish. Top evenly with the bubble and squeak mash and sprinkle over the grated cheese. Bake for 25-30 minutes, until the top is golden and bubbling.
Use up leftover beef as a hearty filling for these delicious Cornish pasties.