60g (2oz) butter, plus extra for greasing 1 onion, sliced 2 garlic cloves, crushed 1kg (2lb) floury potatoes, thinly sliced 375g (12oz) celeriac, peeled and thinly sliced 300ml (1/2 pint) single cream 150ml (1/4 pint) milk 250g (8oz) ricotta cheese 3tbsp snipped fresh chives salt and black pepper 2tbsp fresh breadcrumbs 3tbsp grated Parmesan cheese, plus extra for serving.

1- Melt the butter in a frying pan, add the sliced onion and crushed garlic, and cook gently, stirring occasionally, for 3-5 minutes until softened but not coloured. Lightly butter a large gratin dis.
2- Arrange the potatoes, celeriac, and the onion mixture in layers in the prepared gratin dish, finishing with a neat layer of potatoes.
3- In a large bowl, combine the cream, milk, ricotta cheese, and chives, and season with salt and pepper. Beat well together, then pour over the vegetables.
4- In a small bowl, combine the breadcrumbs and 3tbsp grated Parmesan cheese, and then sprinkle evenly over the potatoes.
5- Bake in a preheated oven at 180ْC (350ْF, Gas 4) for about 1 hour or until the potatoes and celeriac are tender and the top is golden brown.
6- Serve the gratin hot, sprinkled with extra grated Parmesan cheese.