Leek gratin with crispy leek topping

Instructions

1. Step 1

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

2. Step 2

   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.

3. Step 3

   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.

4. Step 4

   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.

5. Step 5

   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.