- 50g/1¾oz butter, plus extra for greasing
- 2 onions, finely sliced
- 1 celeriac, cut into 0.5cm/½in thick slices
- 500g/1lb 1oz potatoes, cut into 0.5cm/½in thick slices
- 600ml/1 pint 1 fl oz hot chicken stock (vegetarians can substitute vegetable stock)
- salt and freshly ground black pepper
- Preheat the oven to 200C/450F/Gas 6.
- Heat a frying pan until hot then add half the butter and all the onions.
- Sweat for 3-4 minutes until just softened.
- Place a layer of celeriac slices into the bottom of a buttered ovenproof dish.
- Top with a layer of onions, then potatoes, then onions again, seasoning with salt and freshly ground black pepper as you go.
- Repeat with the remaining celeriac, onions and potatoes, finishing with a layer of potatoes.
- Dot with the remaining butter.
- Pour over the hot stock so all the layers are covered.
- Transfer to the oven and cook for 45-60 minutes, checking occasionally to make sure the stock hasn't completely evaporated, and pressing the layers down with the back of a spoon.
- Bake until nearly all the stock is absorbed and the top layer is golden brown.
- Serve.