Heat the olive oil in a large saucepan over a medium-low heat. When hot, add the onion and celery. Fry gently for about 5 minutes until softened, adding a little water if the veg look a little dry.
Stir in the celeriac and stock and simmer for 20 minutes, until the celeriac is completely soft.
In the meantime, put all of the gremolata ingredients into a food processor and pulse until finely chopped. Add a little water (up to 1 tbsp) to let down the consistency of the gremolata, if preferred.
Using a free-standing or stick blender, blitz the soup until smooth and creamy. Serve topped with a dollop of gremolata and a sprinkling of pepper.
Recipe extracted from The Breast Cancer Cookbook by Professor Mohammed Keshtgar (Quadrille £20) Photography: Jan Baldwin