Cheesy leeks

• leeks (about 3 medium)↗600g g

  trimmed and sliced into 2 cm rounds

• butter↗50g g
• plain flour↗50g g
• milk↗500ml ml
• mature cheddar↗100g g

  grated

• English mustard↗1 tsp tsp
• stale bread50g g

  ground into crumbs

• thyme leaves↗2 tsp tsp

Step-by-step instructions

1. 1

   Preheat the oven to 220 °C/200 °C with convection/gas 7. Transfer the leeks to a steamer and steam for 6‑8 minutes, until they become bright green and only slightly tender.

2. 2

   Meanwhile, melt butter with flour in a saucepan, stirring constantly until a thick roux forms. Gradually add the milk, drop by drop, stirring continuously until all the milk is incorporated. Cook for another 2‑3 minutes until the sauce thickens enough to coat the back of a spoon. Add most of the grated mature cheddar, mustard, and a little seasoning.

3. 3

   Gently fold the steamed leeks into the cheese sauce, then transfer everything to an oven‑proof baking dish. Sprinkle with breadcrumbs, thyme leaves, and the remaining cheese, then bake for 20 minutes until the top is golden, crisp and bubbles appear at the edges. Let stand for 5 minutes before serving.