Sweet potato lasagne

1. Heat half the oil in a large pan or dish with a lid over a medium-high heat, and fry the mince for 10 minutes until fully browned; use a wooden spoon to break it up as you go. Season with salt and pepper, remove from the pan and set aside.
2. Add the remaining oil to the pan and tip in the veg and pancetta. Cook for 10 minutes until the onion has softened. Turn up the heat and cook for three more minutes or until the pancetta begins to brown.
3. Add the herbs, tomato purée and browned meat back to the pan. Stir to combine.
4. Add the wine and simmer until it evaporates.
5. Add the chopped tomatoes, passata and stock.
6. Give everything a good stir and reduce the heat to low. Leave to simmer for about one hour, or until thickened and reduced, stirring occasionally.
7. While the ragù cooks, make your white sauce. Melt the butter in a large pot over a medium-high heat. Once melted, add the flour and quickly whisk into the butter.
8. Add about one quarter of the milk and whisk quickly to combine. As soon as it has combined, add another quarter of the milk. Repeat until the milk is used up; you may need more or less depending on how thick you want the sauce.
9. Reduce the heat to low and add the cheese, whisking until melted. Season to taste.
10. Once the ragù is ready, preheat the oven to 190˚C/170˚C fan/gas mark 5.
11. To build your lasagne, spoon a quarter of the ragù into a large deep ovenproof dish (roughly 25cm x 30cm) and spread it out evenly.
12. Add a handful of baby spinach leaves – no need to cover the sauce entirely, a scattering with do the trick.
13. Set aside the largest pieces of sweet potato for the top layer, then arrange a third of the sweet potato slices in the baking dish in an even layer, overlapping them
slightly as needed, making sure they completely cover the sauce in one layer. Spread over a layer of white sauce. Repeat this three times, finishing with a layer of white sauce.
14. Sprinkle with the grated cheddar and arrange the mozzarella slices over. Cover with tin foil and bake for 40 minutes. Remove the foil and bake, uncovered, for a further 10-15 minutes until golden brown and cooked through.
15. Remove the lasagne from the oven and leave to sit for 5-10 minutes before serving with salad and garlic bread.