step 1
Bring a large pan of boiling water to the boil.
step 2
Add the celeriac and simmer for 20 mins until soft.
step 3
Drain well and place in a bowl with the butterbeans, butter and yoghurt. Season with a pinch of salt and plenty of black pepper.
step 4
Mash until smooth and creamy, then sprinkle with parsley.