Working with the aubergines one at a time, carefully hold over the lit ring of a gas hob using tongs, turning until deeply charred all over. Or, heat the grill to its highest setting and char the aubergines on a baking tray, turning occasionally until completely blackened, about 15 mins. (If you have a kitchen blowtorch, you can also use this to char the aubergines, though it won’t create the same smoky flavour.) Transfer the aubergines to a plate and leave to cool. When cool enough to handle, peel off the charred skin and remove the stem. Roughly chop the flesh into chunks and set aside.

Heat the oil in a large pan over a low heat and cook the onions with a pinch of salt for 10-15 mins until softened and translucent. Add the garlic and cook for 3 mins more, then add the harissa, coriander seeds, tomatoes and tomato purée. Bring to a simmer and stir in the sugar, vinegar and aubergine flesh. Season and cook, uncovered, for 10 mins, stirring often. Add the dried mint and parsley, remove from the heat and set aside.

For the béchamel, warm the milk in a pan over a low heat until steaming. Melt the butter in a large saucepan, then stir through the flour and cook for 3 mins. Remove from the heat and slowly add the warm milk, whisking continuously. Return to a low heat, bring to a simmer and whisk continuously until thickened. Add 120g of the cheddar and some salt to taste. Stir to melt the cheese.

Heat the oven to 200C/180C fan/gas 6. Spread a spoonful each of the béchamel and ragu into the base of a deep baking dish (about 21 x 30cm). Arrange a layer of lasagne sheets on top, followed by both sauces again and a layer of mozzarella. Repeat until you’ve used all the lasagne sheets and ragu, finishing on a final layer of béchamel, mozzarella and the remaining cheddar. Once cool, will keep well wrapped and frozen for up to four weeks. Defrost at room temperature before baking. Bake for 40-45 mins, then cool for 10 mins before serving.