Quarter your celeriac. Carve off the skin. Cut into 2-3 cm chunks. Halve, peel and finely chop your onion. Finely chop or grate your garlic.
Set a large pan over a high heat to warm for a few mins. Add 1 tbsp oil to the pan, followed by the veg and garlic. Season well. Pour in 1 ltr boiling water. Add the stock cube. Simmer for 20 mins or till the celeriac is tender.
Peel, core and roughly chop your pears. Roughly chop your parsley. Zest your lemon. Blend the celeriac mix with the pears, parsley, the lemon zest and a squeeze of lemon juice. Add more seasoning and lemon juice to taste.