For the soup
1. Remove the knobbly root end off the bottom of the celeriac and cut a flat edge on the opposite side. Lay the celeriac flat onto the chopping board and peel around the outside using a knife.You can use a peeler but the skin will often be too thick for most peelers. Once peeled, cut into quarters and cut each of those quarters into thin slices.
2. Plate a pot large enough to hold 4 litres onto the stove and add some olive oil or brown butter. Add the sliced shallots to the pan along with a few sprigs of thyme. You can tie the thyme branches together with a piece of string to make them easier to remove from the soup later. Season with a pinch of salt and cook over medium heat for 10 minutes while stirring occasionally.
3. Once the shallots have taken on a golden hue, add the sliced garlic and the sliced celery and continue to cook while stirring for 3 minutes or so to take the raw edge off of the garlic.
4. Add the sliced celeriac to the pot and stir to coat with the other vegetables. Season liberally with salt. Turn the heat up to high and add 1.5 litres of water, chicken or vegetable stock.
Water will give you a cleaner flavour while chicken stock will give you the richest soup.
5. Bring up to the boil and cook with the lid on for 10 minutes. Remove the lid and stir. Continue to cook for 15 more minutes or until the celeriac is so tender enough that it can be crushed with the back of a spoon.
6. To finish either insert an immersion blender into the pot or carefully add the contents of your pot in batches into a blender. Add the brown butter, a squeeze of lemon juice and blend on high. Adjust the seasoning with salt and the consistency with more stock or water. Blend for a few minutes until the soup is a silky smooth puree. For an extra luxurious finish, pass the soup through a fine meshed strainer.
For Sauteed Celeriac
7. Cut the celeriac into small cubes, roughly 1cm wide. Quickly saute over medium high heat with 2 tablespoons of brown butter or olive oil, 2 sprigs of thyme and a pinch of salt. Stir constantly until they are browned nicely. Remove from the pan and lay them out onto some paper towels to absorb excess fat.
8. Alternatively cut the cubes slightly larger, season well with olive oil and salt and place onto a lined baking tray and into an oven set to 180C. Roast for 20 minutes or until the celeriac is cooked through and browned.