Ham and cheese bake

Method

1. Heat the oven to 180°C fan/gas 6. Heat the oil and butter in a large lidded pan over a medium heat. Add the leek and cook for 5 minutes until softened. Add the garlic and cook for another 2 minutes, then add the greens, herbs (if using), lemon zest and juice along with some seasoning. Cover and cook for 3-4 minutes until the greens are wilted (you may need to add them in batches). Stir in the ham, then transfer to a large casserole or baking dish. Set aside.
2. For the béchamel, melt the butter in a large pan over amedium-high heat. Add the flour and cook, stirring, for 1 minute. Whisk in the milk off the heat, a little at a time to avoid lumps, then return to the heat and cook, whisking, until the sauce comes to the boil and thickens – about 6-7 minutes. Remove from the heat and stir in the remaining béchamel ingredients.
3. Pour the béchamel over the greens and ham, mixing a little so it sinks into the filling. Put the casserole/baking dish on a baking sheet and bake for 30 minutes until bubbling and golden.
4. While the mornay bakes, mixtogether the crushed crisps, nuts and oregano, if using. Sprinkle over the baked mornay just before serving for added crunch.