Haddock & leek au gratin with sweetcorn mash

• potatoes↗350g g

  quartered

• can sweetcorn↗195g g

  in water

• bag ready-washed spinach↗240g g
• leeks↗2

  thickly sliced

• skimmed milk↗300ml ml

  plus 3 tbsp

• unsalted butter↗15g g
• plain flour↗15g g
• English mustard↗½ tsp tsp
• mature reduced-fat cheese↗75g g

  grated

• fillets of skinless haddock↗2 x 125g

Step-by-step instructions

1. 1

   Preheat the oven to 200 °C/180 °C fan/gas 6. Boil the potatoes for 15‑20 minutes until tender, then drain. Reserve 3 tbsp of corn and blend the rest (with its juice) using a hand blender or food processor until completely smooth, then mash into the potatoes. Cook the spinach according to the package instructions – if you have a microwave, use that method.

2. 2

   Place the leeks in a pan with the 300 ml milk and butter. Cook gently, partially covered, for 8 minutes until the leeks are tender. (Watch carefully as the milk can easily boil over.) Mix the 3 tbsp milk with the flour and mustard, then stir into the leek mixture – keep stirring until thickened. Remove from heat and stir in three‑quarters of the cheese.

3. 3

   Squeeze as much liquid as possible from the spinach, then spread it on the base of two gratin dishes. Place a fish fillet on top of each, then spoon over the leek‑cheese sauce. Top with the sweetcorn mash. Mix the remaining corn and cheese and scatter on top. Place the dishes on a baking tray and bake for 25 minutes until the fish flakes when tested and the top is golden.