Peel and clean celeriac. cut into small cubes and place into water with some lemon juice

clean and peel potatoes. cut into small cubes

clean, peel and chop onion, leeks and garlic

in a pot, add butter, onions, leeks and garlic and fry lightly until soft

add potatoes and celeriac

poor in chicken stock and then enough water to just cover

bring to the boil then simmer for 30 min out until potatoes and celeriac are soft

blend with a stick blender or kitchen blender adding sour cream

season to taste and serve