Heat the oil and margarine in a large lidded saucepan. Peel and chop the onion and add to the pan, then cook gently for 3-4 minutes until starting to soften.

Peel the celeriac and potato and cut both into 1cm cubes then add to the pan. Season well with salt and black pepper, then cover and cook over a gentle heat for 6-8 minutes, stirring regularly.

Add the water, stock cube and pick the thyme leaves, (picked from the stalks), then bring to the boil and reduce to a simmer. Cook for 15-20 minutes until the celeriac and potato are very well cooked through.

Add the hazelnut milk, then tip into a high-speed blender or use a hand blender to blitz to a very smooth and velvety puree. Return to the pan and heat through until piping hot, then serve drizzled with a little dairy-free cream, roughly chopped hazelnuts and a few thyme leaves.