- olive oil
- 450g/1lb plain flour
- 1 tsp bicarbonate of soda
- 1 tsp salt
- 400ml/14fl oz (approx) buttermilk
- pinch Maldon sea salt
- 30g/1oz butter
- 110g/4oz onions, finely chipped
- 140g/5oz potatoes, finely
- salt and freshly ground black pepper
- 425g/15oz celeriac, finely diced
- 1.2 litres/2 pints chicken stock (vegetarians may substitute with vegetable stock or water)
- 170ml/6fl oz milk
- 60ml/2fl oz cream (optional)
- fresh flatleaf parsley, chopped, to garnish
- 25g/1oz toasted hazelnuts, chopped for garnish
- Preheat the oven 230C/450F/Gas 8. Brush a baking sheet generously with olive oil.
- For the soda bread, sift the plain flour and the bicarbonate of soda into a big bowl. Add the salt, and mix with your hands. Make a well in the centre of the flour mix, pour in most of the buttermilk, and with one hand stiff and your fingers spread out like a claw, start mixing in a full circle once the butter milk has gone in.
- Keep mixing like this until you have a soft dough. Do not knead it but work it very gently to bring it together.
- Transfer to a floured surface, and roll it out to about 35x20cm/14x8in and transfer it to the oiled tray.
- Brush the top of the dough with some more oil and sprinkle with a little sea salt. Transfer to the oven and cook for ten minutes. Then turn the oven down to 200C/400F/Gas 6 and cook for a further 8-12 minutes until cooked. When cooked, it should feel firm in the centre and be golden brown.
- Transfer the soda bread from the oven to a wire rack and cool for a couple of minutes, then cut it into squares to serve.
- Meanwhile for the soup, melt the butter in a heavy saucepan over a medium heat. When it foams, add the potatoes and onions and toss them in the butter until evenly coated. Season with salt and freshly ground pepper.
- Cover with a circle of baking paper (to keep in the steam) and the saucepan lid, and sweat over a gentle heat for about ten minutes, until the vegetables are soft but not coloured.
- Remove the paper lid. Add the celeriac and chicken stock, bring to the boil, reduce the heat and simmer for 8-10 minutes, until the celeriac is soft.
- Liquidise the soup using a hand blender, adding a little more stock, milk (or cream) to thin to the required consistency. Season to taste with salt and freshly ground black pepper.
- Serve the soup piping hot in a bowl with a scattering of chopped hazelnuts, and a little chopped parsley to garnish, accompanied by slices of soda bread.