Leek gratin with crispy leek topping

Cut most of the leeks into 3cm pieces, finely slicing 10cm of the white part of one leek for the topping.

Steam the bite-sized pieces for 6-8 mins, or until just tender, then leave to steam-dry. Meanwhile, heat the oil in a frying pan over a medium heat and fry the finely sliced leek for 15-18 mins, stirring regularly until crisp and golden. Scoop onto kitchen paper to drain, and season with salt. Keep the oil in the pan to one side, off the heat.

Heat the oven to 200C/180C fan/gas 6. Warm the flour and butter in a pan until they form a thick brown paste, then gradually add the milk, a splash at a time, stirring until a smooth sauce forms. Stir in the mustard, bay leaves and most of the cheddar. Season with salt and pepper.

Stir the steamed leeks into the sauce and transfer to an ovenproof dish. Scatter over the remaining cheese and bake for 35-40 mins until bubbling and golden on top.

Reheat the reserved oil over a medium heat and fry the breadcrumbs for 4-5 mins, or until golden brown and crisp. Drain on kitchen paper. Stir together the crispy leeks, breadcrumbs, thyme leaves and zest in a bowl with some seasoning. Once the gratin comes out of the oven, scatter over the crispy leek and breadcrumb topping.