Cheesy celeriac, leek and rosemary gratin

• butter↗25g g
• leeks↗2

  outer layer removed, washed and sliced into rings

• rosemary leavessmall handful

  coarsely chopped

• bay leaf↗1
• cream↗300ml ml
• milk↗300ml ml
• celeriac↗1

  (about 500 g), peeled, quartered and thinly sliced

• cheddar↗100g g

  or gruyère, coarsely grated

Step-by-step instructions

1. 1

   Melt the butter in a saucepan. Add the leeks, rosemary and bay leaf, cover and cook over very low medium heat for 15‑20 minutes until the leeks become soft. Pour in the milk and almost all of the cream, then season and bring to a boil. Remove from heat, let cool slightly, then remove the bay leaf.

2. 2

   Pour a little of the leek mixture into a heat‑proof gratin dish. Lay a layer of celeriac, then season. Add more of the leek mixture and sprinkle some cheese. Repeat the process, alternating layers of leek mixture, cheese and celeriac slices, finishing with a pour of cream and the remaining cheese. It can be prepared up to a day ahead and stored in the refrigerator.

3. 3

   Preheat the oven to 180 °C/160 °C with convection/gas 4. Bake the gratin for 1 hour to 1 hour 15 minutes, until the top is golden and the celeriac is tender when pierced with a knife. If the gratin browns too much, cover the dish with foil. It can be cooled and then reheated in the microwave or oven on low heat, adding a little more cream.